INSTRUCTORS Raffi Hovasapian John Zhu

Home » Mathematics » AP Calculus AB » Volumes II: Volumes by Washers

Raffi Hovasapian

Raffi Hovasapian

Volumes II: Volumes by Washers

Slide Duration:

Table of Contents

Section 1: Limits and Derivatives
Overview & Slopes of Curves

42m 8s

Intro
0:00
Overview & Slopes of Curves
0:21
Differential and Integral
0:22
Fundamental Theorem of Calculus
6:36
Differentiation or Taking the Derivative
14:24
What Does the Derivative Mean and How do We Find it?
15:18
Example: f'(x)
19:24
Example: f(x) = sin (x)
29:16
General Procedure for Finding the Derivative of f(x)
37:33
More on Slopes of Curves

50m 53s

Intro
0:00
Slope of the Secant Line along a Curve
0:12
Slope of the Tangent Line to f(x) at a Particlar Point
0:13
Slope of the Secant Line along a Curve
2:59
Instantaneous Slope
6:51
Instantaneous Slope
6:52
Example: Distance, Time, Velocity
13:32
Instantaneous Slope and Average Slope
25:42
Slope & Rate of Change
29:55
Slope & Rate of Change
29:56
Example: Slope = 2
33:16
Example: Slope = 4/3
34:32
Example: Slope = 4 (m/s)
39:12
Example: Density = Mass / Volume
40:33
Average Slope, Average Rate of Change, Instantaneous Slope, and Instantaneous Rate of Change
47:46
Example Problems for Slopes of Curves

59m 12s

Intro
0:00
Example I: Water Tank
0:13
Part A: Which is the Independent Variable and Which is the Dependent?
2:00
Part B: Average Slope
3:18
Part C: Express These Slopes as Rates-of-Change
9:28
Part D: Instantaneous Slope
14:54
Example II: y = √(x-3)
28:26
Part A: Calculate the Slope of the Secant Line
30:39
Part B: Instantaneous Slope
41:26
Part C: Equation for the Tangent Line
43:59
Example III: Object in the Air
49:37
Part A: Average Velocity
50:37
Part B: Instantaneous Velocity
55:30
Desmos Tutorial

18m 43s

Intro
0:00
Desmos Tutorial
1:42
Desmos Tutorial
1:43
Things You Must Learn To Do on Your Particular Calculator
2:39
Things You Must Learn To Do on Your Particular Calculator
2:40
Example I: y=sin x
4:54
Example II: y=x³ and y = d/(dx) (x³)
9:22
Example III: y = x² {-5 <= x <= 0} and y = cos x {0 < x < 6}
13:15
The Limit of a Function

51m 53s

Intro
0:00
The Limit of a Function
0:14
The Limit of a Function
0:15
Graph: Limit of a Function
12:24
Table of Values
16:02
lim x→a f(x) Does not Say What Happens When x = a
20:05
Example I: f(x) = x²
24:34
Example II: f(x) = 7
27:05
Example III: f(x) = 4.5
30:33
Example IV: f(x) = 1/x
34:03
Example V: f(x) = 1/x²
36:43
The Limit of a Function, Cont.
38:16
Infinity and Negative Infinity
38:17
Does Not Exist
42:45
Summary
46:48
Example Problems for the Limit of a Function

24m 43s

Intro
0:00
Example I: Explain in Words What the Following Symbols Mean
0:10
Example II: Find the Following Limit
5:21
Example III: Use the Graph to Find the Following Limits
7:35
Example IV: Use the Graph to Find the Following Limits
11:48
Example V: Sketch the Graph of a Function that Satisfies the Following Properties
15:25
Example VI: Find the Following Limit
18:44
Example VII: Find the Following Limit
20:06
Calculating Limits Mathematically

53m 48s

Intro
0:00
Plug-in Procedure
0:09
Plug-in Procedure
0:10
Limit Laws
9:14
Limit Law 1
10:05
Limit Law 2
10:54
Limit Law 3
11:28
Limit Law 4
11:54
Limit Law 5
12:24
Limit Law 6
13:14
Limit Law 7
14:38
Plug-in Procedure, Cont.
16:35
Plug-in Procedure, Cont.
16:36
Example I: Calculating Limits Mathematically
20:50
Example II: Calculating Limits Mathematically
27:37
Example III: Calculating Limits Mathematically
31:42
Example IV: Calculating Limits Mathematically
35:36
Example V: Calculating Limits Mathematically
40:58
Limits Theorem
44:45
Limits Theorem 1
44:46
Limits Theorem 2: Squeeze Theorem
46:34
Example VI: Calculating Limits Mathematically
49:26
Example Problems for Calculating Limits Mathematically

21m 22s

Intro
0:00
Example I: Evaluate the Following Limit by Showing Each Application of a Limit Law
0:16
Example II: Evaluate the Following Limit
1:51
Example III: Evaluate the Following Limit
3:36
Example IV: Evaluate the Following Limit
8:56
Example V: Evaluate the Following Limit
11:19
Example VI: Calculating Limits Mathematically
13:19
Example VII: Calculating Limits Mathematically
14:59
Calculating Limits as x Goes to Infinity

50m 1s

Intro
0:00
Limit as x Goes to Infinity
0:14
Limit as x Goes to Infinity
0:15
Let's Look at f(x) = 1 / (x-3)
1:04
Summary
9:34
Example I: Calculating Limits as x Goes to Infinity
12:16
Example II: Calculating Limits as x Goes to Infinity
21:22
Example III: Calculating Limits as x Goes to Infinity
24:10
Example IV: Calculating Limits as x Goes to Infinity
36:00
Example Problems for Limits at Infinity

36m 31s

Intro
0:00
Example I: Calculating Limits as x Goes to Infinity
0:14
Example II: Calculating Limits as x Goes to Infinity
3:27
Example III: Calculating Limits as x Goes to Infinity
8:11
Example IV: Calculating Limits as x Goes to Infinity
14:20
Example V: Calculating Limits as x Goes to Infinity
20:07
Example VI: Calculating Limits as x Goes to Infinity
23:36
Continuity

53m

Intro
0:00
Definition of Continuity
0:08
Definition of Continuity
0:09
Example: Not Continuous
3:52
Example: Continuous
4:58
Example: Not Continuous
5:52
Procedure for Finding Continuity
9:45
Law of Continuity
13:44
Law of Continuity
13:45
Example I: Determining Continuity on a Graph
15:55
Example II: Show Continuity & Determine the Interval Over Which the Function is Continuous
17:57
Example III: Is the Following Function Continuous at the Given Point?
22:42
Theorem for Composite Functions
25:28
Theorem for Composite Functions
25:29
Example IV: Is cos(x³ + ln x) Continuous at x=π/2?
27:00
Example V: What Value of A Will make the Following Function Continuous at Every Point of Its Domain?
34:04
Types of Discontinuity
39:18
Removable Discontinuity
39:33
Jump Discontinuity
40:06
Infinite Discontinuity
40:32
Intermediate Value Theorem
40:58
Intermediate Value Theorem: Hypothesis & Conclusion
40:59
Intermediate Value Theorem: Graphically
43:40
Example VI: Prove That the Following Function Has at Least One Real Root in the Interval [4,6]
47:46
Derivative I

40m 2s

Intro
0:00
Derivative
0:09
Derivative
0:10
Example I: Find the Derivative of f(x)=x³
2:20
Notations for the Derivative
7:32
Notations for the Derivative
7:33
Derivative & Rate of Change
11:14
Recall the Rate of Change
11:15
Instantaneous Rate of Change
17:04
Graphing f(x) and f'(x)
19:10
Example II: Find the Derivative of x⁴ - x²
24:00
Example III: Find the Derivative of f(x)=√x
30:51
Derivatives II

53m 45s

Intro
0:00
Example I: Find the Derivative of (2+x)/(3-x)
0:18
Derivatives II
9:02
f(x) is Differentiable if f'(x) Exists
9:03
Recall: For a Limit to Exist, Both Left Hand and Right Hand Limits Must Equal to Each Other
17:19
Geometrically: Differentiability Means the Graph is Smooth
18:44
Example II: Show Analytically that f(x) = |x| is Nor Differentiable at x=0
20:53
Example II: For x > 0
23:53
Example II: For x < 0
25:36
Example II: What is f(0) and What is the lim |x| as x→0?
30:46
Differentiability & Continuity
34:22
Differentiability & Continuity
34:23
How Can a Function Not be Differentiable at a Point?
39:38
How Can a Function Not be Differentiable at a Point?
39:39
Higher Derivatives
41:58
Higher Derivatives
41:59
Derivative Operator
45:12
Example III: Find (dy)/(dx) & (d²y)/(dx²) for y = x³
49:29
More Example Problems for The Derivative

31m 38s

Intro
0:00
Example I: Sketch f'(x)
0:10
Example II: Sketch f'(x)
2:14
Example III: Find the Derivative of the Following Function sing the Definition
3:49
Example IV: Determine f, f', and f'' on a Graph
12:43
Example V: Find an Equation for the Tangent Line to the Graph of the Following Function at the Given x-value
13:40
Example VI: Distance vs. Time
20:15
Example VII: Displacement, Velocity, and Acceleration
23:56
Example VIII: Graph the Displacement Function
28:20
Section 2: Differentiation
Differentiation of Polynomials & Exponential Functions

47m 35s

Intro
0:00
Differentiation of Polynomials & Exponential Functions
0:15
Derivative of a Function
0:16
Derivative of a Constant
2:35
Power Rule
3:08
If C is a Constant
4:19
Sum Rule
5:22
Exponential Functions
6:26
Example I: Differentiate
7:45
Example II: Differentiate
12:38
Example III: Differentiate
15:13
Example IV: Differentiate
16:20
Example V: Differentiate
19:19
Example VI: Find the Equation of the Tangent Line to a Function at a Given Point
12:18
Example VII: Find the First & Second Derivatives
25:59
Example VIII
27:47
Part A: Find the Velocity & Acceleration Functions as Functions of t
27:48
Part B: Find the Acceleration after 3 Seconds
30:12
Part C: Find the Acceleration when the Velocity is 0
30:53
Part D: Graph the Position, Velocity, & Acceleration Graphs
32:50
Example IX: Find a Cubic Function Whose Graph has Horizontal Tangents
34:53
Example X: Find a Point on a Graph
42:31
The Product, Power & Quotient Rules

47m 25s

Intro
0:00
The Product, Power and Quotient Rules
0:19
Differentiate Functions
0:20
Product Rule
5:30
Quotient Rule
9:15
Power Rule
10:00
Example I: Product Rule
13:48
Example II: Quotient Rule
16:13
Example III: Power Rule
18:28
Example IV: Find dy/dx
19:57
Example V: Find dy/dx
24:53
Example VI: Find dy/dx
28:38
Example VII: Find an Equation for the Tangent to the Curve
34:54
Example VIII: Find d²y/dx²
38:08
Derivatives of the Trigonometric Functions

41m 8s

Intro
0:00
Derivatives of the Trigonometric Functions
0:09
Let's Find the Derivative of f(x) = sin x
0:10
Important Limits to Know
4:59
d/dx (sin x)
6:06
d/dx (cos x)
6:38
d/dx (tan x)
6:50
d/dx (csc x)
7:02
d/dx (sec x)
7:15
d/dx (cot x)
7:27
Example I: Differentiate f(x) = x² - 4 cos x
7:56
Example II: Differentiate f(x) = x⁵ tan x
9:04
Example III: Differentiate f(x) = (cos x) / (3 + sin x)
10:56
Example IV: Differentiate f(x) = e^x / (tan x - sec x)
14:06
Example V: Differentiate f(x) = (csc x - 4) / (cot x)
15:37
Example VI: Find an Equation of the Tangent Line
21:48
Example VII: For What Values of x Does the Graph of the Function x + 3 cos x Have a Horizontal Tangent?
25:17
Example VIII: Ladder Problem
28:23
Example IX: Evaluate
33:22
Example X: Evaluate
36:38
The Chain Rule

24m 56s

Intro
0:00
The Chain Rule
0:13
Recall the Composite Functions
0:14
Derivatives of Composite Functions
1:34
Example I: Identify f(x) and g(x) and Differentiate
6:41
Example II: Identify f(x) and g(x) and Differentiate
9:47
Example III: Differentiate
11:03
Example IV: Differentiate f(x) = -5 / (x² + 3)³
12:15
Example V: Differentiate f(x) = cos(x² + c²)
14:35
Example VI: Differentiate f(x) = cos⁴x +c²
15:41
Example VII: Differentiate
17:03
Example VIII: Differentiate f(x) = sin(tan x²)
19:01
Example IX: Differentiate f(x) = sin(tan² x)
21:02
More Chain Rule Example Problems

25m 32s

Intro
0:00
Example I: Differentiate f(x) = sin(cos(tanx))
0:38
Example II: Find an Equation for the Line Tangent to the Given Curve at the Given Point
2:25
Example III: F(x) = f(g(x)), Find F' (6)
4:22
Example IV: Differentiate & Graph both the Function & the Derivative in the Same Window
5:35
Example V: Differentiate f(x) = ( (x-8)/(x+3) )⁴
10:18
Example VI: Differentiate f(x) = sec²(12x)
12:28
Example VII: Differentiate
14:41
Example VIII: Differentiate
19:25
Example IX: Find an Expression for the Rate of Change of the Volume of the Balloon with Respect to Time
21:13
Implicit Differentiation

52m 31s

Intro
0:00
Implicit Differentiation
0:09
Implicit Differentiation
0:10
Example I: Find (dy)/(dx) by both Implicit Differentiation and Solving Explicitly for y
12:15
Example II: Find (dy)/(dx) of x³ + x²y + 7y² = 14
19:18
Example III: Find (dy)/(dx) of x³y² + y³x² = 4x
21:43
Example IV: Find (dy)/(dx) of the Following Equation
24:13
Example V: Find (dy)/(dx) of 6sin x cos y = 1
29:00
Example VI: Find (dy)/(dx) of x² cos² y + y sin x = 2sin x cos y
31:02
Example VII: Find (dy)/(dx) of √(xy) = 7 + y²e^x
37:36
Example VIII: Find (dy)/(dx) of 4(x²+y²)² = 35(x²-y²)
41:03
Example IX: Find (d²y)/(dx²) of x² + y² = 25
44:05
Example X: Find (d²y)/(dx²) of sin x + cos y = sin(2x)
47:48
Section 3: Applications of the Derivative
Linear Approximations & Differentials

47m 34s

Intro
0:00
Linear Approximations & Differentials
0:09
Linear Approximations & Differentials
0:10
Example I: Linear Approximations & Differentials
11:27
Example II: Linear Approximations & Differentials
20:19
Differentials
30:32
Differentials
30:33
Example III: Linear Approximations & Differentials
34:09
Example IV: Linear Approximations & Differentials
35:57
Example V: Relative Error
38:46
Related Rates

45m 33s

Intro
0:00
Related Rates
0:08
Strategy for Solving Related Rates Problems #1
0:09
Strategy for Solving Related Rates Problems #2
1:46
Strategy for Solving Related Rates Problems #3
2:06
Strategy for Solving Related Rates Problems #4
2:50
Strategy for Solving Related Rates Problems #5
3:38
Example I: Radius of a Balloon
5:15
Example II: Ladder
12:52
Example III: Water Tank
19:08
Example IV: Distance between Two Cars
29:27
Example V: Line-of-Sight
36:20
More Related Rates Examples

37m 17s

Intro
0:00
Example I: Shadow
0:14
Example II: Particle
4:45
Example III: Water Level
10:28
Example IV: Clock
20:47
Example V: Distance between a House and a Plane
29:11
Maximum & Minimum Values of a Function

40m 44s

Intro
0:00
Maximum & Minimum Values of a Function, Part 1
0:23
Absolute Maximum
2:20
Absolute Minimum
2:52
Local Maximum
3:38
Local Minimum
4:26
Maximum & Minimum Values of a Function, Part 2
6:11
Function with Absolute Minimum but No Absolute Max, Local Max, and Local Min
7:18
Function with Local Max & Min but No Absolute Max & Min
8:48
Formal Definitions
10:43
Absolute Maximum
11:18
Absolute Minimum
12:57
Local Maximum
14:37
Local Minimum
16:25
Extreme Value Theorem
18:08
Theorem: f'(c) = 0
24:40
Critical Number (Critical Value)
26:14
Procedure for Finding the Critical Values of f(x)
28:32
Example I: Find the Critical Values of f(x) x + sinx
29:51
Example II: What are the Absolute Max & Absolute Minimum of f(x) = x + 4 sinx on [0,2π]
35:31
Example Problems for Max & Min

40m 44s

Intro
0:00
Example I: Identify Absolute and Local Max & Min on the Following Graph
0:11
Example II: Sketch the Graph of a Continuous Function
3:11
Example III: Sketch the Following Graphs
4:40
Example IV: Find the Critical Values of f (x) = 3x⁴ - 7x³ + 4x²
6:13
Example V: Find the Critical Values of f(x) = |2x - 5|
8:42
Example VI: Find the Critical Values
11:42
Example VII: Find the Critical Values f(x) = cos²(2x) on [0,2π]
16:57
Example VIII: Find the Absolute Max & Min f(x) = 2sinx + 2cos x on [0,(π/3)]
20:08
Example IX: Find the Absolute Max & Min f(x) = (ln(2x)) / x on [1,3]
24:39
The Mean Value Theorem

25m 54s

Intro
0:00
Rolle's Theorem
0:08
Rolle's Theorem: If & Then
0:09
Rolle's Theorem: Geometrically
2:06
There May Be More than 1 c Such That f'( c ) = 0
3:30
Example I: Rolle's Theorem
4:58
The Mean Value Theorem
9:12
The Mean Value Theorem: If & Then
9:13
The Mean Value Theorem: Geometrically
11:07
Example II: Mean Value Theorem
13:43
Example III: Mean Value Theorem
21:19
Using Derivatives to Graph Functions, Part I

25m 54s

Intro
0:00
Using Derivatives to Graph Functions, Part I
0:12
Increasing/ Decreasing Test
0:13
Example I: Find the Intervals Over Which the Function is Increasing & Decreasing
3:26
Example II: Find the Local Maxima & Minima of the Function
19:18
Example III: Find the Local Maxima & Minima of the Function
31:39
Using Derivatives to Graph Functions, Part II

44m 58s

Intro
0:00
Using Derivatives to Graph Functions, Part II
0:13
Concave Up & Concave Down
0:14
What Does This Mean in Terms of the Derivative?
6:14
Point of Inflection
8:52
Example I: Graph the Function
13:18
Example II: Function x⁴ - 5x²
19:03
Intervals of Increase & Decrease
19:04
Local Maxes and Mins
25:01
Intervals of Concavity & X-Values for the Points of Inflection
29:18
Intervals of Concavity & Y-Values for the Points of Inflection
34:18
Graphing the Function
40:52
Example Problems I

49m 19s

Intro
0:00
Example I: Intervals, Local Maxes & Mins
0:26
Example II: Intervals, Local Maxes & Mins
5:05
Example III: Intervals, Local Maxes & Mins, and Inflection Points
13:40
Example IV: Intervals, Local Maxes & Mins, Inflection Points, and Intervals of Concavity
23:02
Example V: Intervals, Local Maxes & Mins, Inflection Points, and Intervals of Concavity
34:36
Example Problems III

59m 1s

Intro
0:00
Example I: Intervals, Local Maxes & Mins, Inflection Points, Intervals of Concavity, and Asymptotes
0:11
Example II: Intervals, Local Maxes & Mins, Inflection Points, Intervals of Concavity, and Asymptotes
21:24
Example III: Cubic Equation f(x) = Ax³ + Bx² + Cx + D
37:56
Example IV: Intervals, Local Maxes & Mins, Inflection Points, Intervals of Concavity, and Asymptotes
46:19
L'Hospital's Rule

30m 9s

Intro
0:00
L'Hospital's Rule
0:19
Indeterminate Forms
0:20
L'Hospital's Rule
3:38
Example I: Evaluate the Following Limit Using L'Hospital's Rule
8:50
Example II: Evaluate the Following Limit Using L'Hospital's Rule
10:30
Indeterminate Products
11:54
Indeterminate Products
11:55
Example III: L'Hospital's Rule & Indeterminate Products
13:57
Indeterminate Differences
17:00
Indeterminate Differences
17:01
Example IV: L'Hospital's Rule & Indeterminate Differences
18:57
Indeterminate Powers
22:20
Indeterminate Powers
22:21
Example V: L'Hospital's Rule & Indeterminate Powers
25:13
Example Problems for L'Hospital's Rule

38m 14s

Intro
0:00
Example I: Evaluate the Following Limit
0:17
Example II: Evaluate the Following Limit
2:45
Example III: Evaluate the Following Limit
6:54
Example IV: Evaluate the Following Limit
8:43
Example V: Evaluate the Following Limit
11:01
Example VI: Evaluate the Following Limit
14:48
Example VII: Evaluate the Following Limit
17:49
Example VIII: Evaluate the Following Limit
20:37
Example IX: Evaluate the Following Limit
25:16
Example X: Evaluate the Following Limit
32:44
Optimization Problems I

49m 59s

Intro
0:00
Example I: Find the Dimensions of the Box that Gives the Greatest Volume
1:23
Fundamentals of Optimization Problems
18:08
Fundamental #1
18:33
Fundamental #2
19:09
Fundamental #3
19:19
Fundamental #4
20:59
Fundamental #5
21:55
Fundamental #6
23:44
Example II: Demonstrate that of All Rectangles with a Given Perimeter, the One with the Largest Area is a Square
24:36
Example III: Find the Points on the Ellipse 9x² + y² = 9 Farthest Away from the Point (1,0)
35:13
Example IV: Find the Dimensions of the Rectangle of Largest Area that can be Inscribed in a Circle of Given Radius R
43:10
Optimization Problems II

55m 10s

Intro
0:00
Example I: Optimization Problem
0:13
Example II: Optimization Problem
17:34
Example III: Optimization Problem
35:06
Example IV: Revenue, Cost, and Profit
43:22
Newton's Method

30m 22s

Intro
0:00
Newton's Method
0:45
Newton's Method
0:46
Example I: Find x2 and x3
13:18
Example II: Use Newton's Method to Approximate
15:48
Example III: Find the Root of the Following Equation to 6 Decimal Places
19:57
Example IV: Use Newton's Method to Find the Coordinates of the Inflection Point
23:11
Section 4: Integrals
Antiderivatives

55m 26s

Intro
0:00
Antiderivatives
0:23
Definition of an Antiderivative
0:24
Antiderivative Theorem
7:58
Function & Antiderivative
12:10
x^n
12:30
1/x
13:00
e^x
13:08
cos x
13:18
sin x
14:01
sec² x
14:11
secxtanx
14:18
1/√(1-x²)
14:26
1/(1+x²)
14:36
-1/√(1-x²)
14:45
Example I: Find the Most General Antiderivative for the Following Functions
15:07
Function 1: f(x) = x³ -6x² + 11x - 9
15:42
Function 2: f(x) = 14√(x) - 27 4√x
19:12
Function 3: (fx) = cos x - 14 sinx
20:53
Function 4: f(x) = (x⁵+2√x )/( x^(4/3) )
22:10
Function 5: f(x) = (3e^x) - 2/(1+x²)
25:42
Example II: Given the Following, Find the Original Function f(x)
26:37
Function 1: f'(x) = 5x³ - 14x + 24, f(2) = 40
27:55
Function 2: f'(x) 3 sinx + sec²x, f(π/6) = 5
30:34
Function 3: f''(x) = 8x - cos x, f(1.5) = 12.7, f'(1.5) = 4.2
32:54
Function 4: f''(x) = 5/(√x), f(2) 15, f'(2) = 7
37:54
Example III: Falling Object
41:58
Problem 1: Find an Equation for the Height of the Ball after t Seconds
42:48
Problem 2: How Long Will It Take for the Ball to Strike the Ground?
48:30
Problem 3: What is the Velocity of the Ball as it Hits the Ground?
49:52
Problem 4: Initial Velocity of 6 m/s, How Long Does It Take to Reach the Ground?
50:46
The Area Under a Curve

51m 3s

Intro
0:00
The Area Under a Curve
0:13
Approximate Using Rectangles
0:14
Let's Do This Again, Using 4 Different Rectangles
9:40
Approximate with Rectangles
16:10
Left Endpoint
18:08
Right Endpoint
25:34
Left Endpoint vs. Right Endpoint
30:58
Number of Rectangles
34:08
True Area
37:36
True Area
37:37
Sigma Notation & Limits
43:32
When You Have to Explicitly Solve Something
47:56
Example Problems for Area Under a Curve

33m 7s

Intro
0:00
Example I: Using Left Endpoint & Right Endpoint to Approximate Area Under a Curve
0:10
Example II: Using 5 Rectangles, Approximate the Area Under the Curve
11:32
Example III: Find the True Area by Evaluating the Limit Expression
16:07
Example IV: Find the True Area by Evaluating the Limit Expression
24:52
The Definite Integral

43m 19s

Intro
0:00
The Definite Integral
0:08
Definition to Find the Area of a Curve
0:09
Definition of the Definite Integral
4:08
Symbol for Definite Integral
8:45
Regions Below the x-axis
15:18
Associating Definite Integral to a Function
19:38
Integrable Function
27:20
Evaluating the Definite Integral
29:26
Evaluating the Definite Integral
29:27
Properties of the Definite Integral
35:24
Properties of the Definite Integral
35:25
Example Problems for The Definite Integral

32m 14s

Intro
0:00
Example I: Approximate the Following Definite Integral Using Midpoints & Sub-intervals
0:11
Example II: Express the Following Limit as a Definite Integral
5:28
Example III: Evaluate the Following Definite Integral Using the Definition
6:28
Example IV: Evaluate the Following Integral Using the Definition
17:06
Example V: Evaluate the Following Definite Integral by Using Areas
25:41
Example VI: Definite Integral
30:36
The Fundamental Theorem of Calculus

24m 17s

Intro
0:00
The Fundamental Theorem of Calculus
0:17
Evaluating an Integral
0:18
Lim as x → ∞
12:19
Taking the Derivative
14:06
Differentiation & Integration are Inverse Processes
15:04
1st Fundamental Theorem of Calculus
20:08
1st Fundamental Theorem of Calculus
20:09
2nd Fundamental Theorem of Calculus
22:30
2nd Fundamental Theorem of Calculus
22:31
Example Problems for the Fundamental Theorem

25m 21s

Intro
0:00
Example I: Find the Derivative of the Following Function
0:17
Example II: Find the Derivative of the Following Function
1:40
Example III: Find the Derivative of the Following Function
2:32
Example IV: Find the Derivative of the Following Function
5:55
Example V: Evaluate the Following Integral
7:13
Example VI: Evaluate the Following Integral
9:46
Example VII: Evaluate the Following Integral
12:49
Example VIII: Evaluate the Following Integral
13:53
Example IX: Evaluate the Following Graph
15:24
Local Maxs and Mins for g(x)
15:25
Where Does g(x) Achieve Its Absolute Max on [0,8]
20:54
On What Intervals is g(x) Concave Up/Down?
22:20
Sketch a Graph of g(x)
24:34
More Example Problems, Including Net Change Applications

34m 22s

Intro
0:00
Example I: Evaluate the Following Indefinite Integral
0:10
Example II: Evaluate the Following Definite Integral
0:59
Example III: Evaluate the Following Integral
2:59
Example IV: Velocity Function
7:46
Part A: Net Displacement
7:47
Part B: Total Distance Travelled
13:15
Example V: Linear Density Function
20:56
Example VI: Acceleration Function
25:10
Part A: Velocity Function at Time t
25:11
Part B: Total Distance Travelled During the Time Interval
28:38
Solving Integrals by Substitution

27m 20s

Intro
0:00
Table of Integrals
0:35
Example I: Evaluate the Following Indefinite Integral
2:02
Example II: Evaluate the Following Indefinite Integral
7:27
Example IIII: Evaluate the Following Indefinite Integral
10:57
Example IV: Evaluate the Following Indefinite Integral
12:33
Example V: Evaluate the Following
14:28
Example VI: Evaluate the Following
16:00
Example VII: Evaluate the Following
19:01
Example VIII: Evaluate the Following
21:49
Example IX: Evaluate the Following
24:34
Section 5: Applications of Integration
Areas Between Curves

34m 56s

Intro
0:00
Areas Between Two Curves: Function of x
0:08
Graph 1: Area Between f(x) & g(x)
0:09
Graph 2: Area Between f(x) & g(x)
4:07
Is It Possible to Write as a Single Integral?
8:20
Area Between the Curves on [a,b]
9:24
Absolute Value
10:32
Formula for Areas Between Two Curves: Top Function - Bottom Function
17:03
Areas Between Curves: Function of y
17:49
What if We are Given Functions of y?
17:50
Formula for Areas Between Two Curves: Right Function - Left Function
21:48
Finding a & b
22:32
Example Problems for Areas Between Curves

42m 55s

Intro
0:00
Instructions for the Example Problems
0:10
Example I: y = 7x - x² and y=x
0:37
Example II: x=y²-3, x=e^((1/2)y), y=-1, and y=2
6:25
Example III: y=(1/x), y=(1/x³), and x=4
12:25
Example IV: 15-2x² and y=x²-5
15:52
Example V: x=(1/8)y³ and x=6-y²
20:20
Example VI: y=cos x, y=sin(2x), [0,π/2]
24:34
Example VII: y=2x², y=10x², 7x+2y=10
29:51
Example VIII: Velocity vs. Time
33:23
Part A: At 2.187 Minutes, Which care is Further Ahead?
33:24
Part B: If We Shaded the Region between the Graphs from t=0 to t=2.187, What Would This Shaded Area Represent?
36:32
Part C: At 4 Minutes Which Car is Ahead?
37:11
Part D: At What Time Will the Cars be Side by Side?
37:50
Volumes I: Slices

34m 15s

Intro
0:00
Volumes I: Slices
0:18
Rotate the Graph of y=√x about the x-axis
0:19
How can I use Integration to Find the Volume?
3:16
Slice the Solid Like a Loaf of Bread
5:06
Volumes Definition
8:56
Example I: Find the Volume of the Solid Obtained by Rotating the Region Bounded by the Given Functions about the Given Line of Rotation
12:18
Example II: Find the Volume of the Solid Obtained by Rotating the Region Bounded by the Given Functions about the Given Line of Rotation
19:05
Example III: Find the Volume of the Solid Obtained by Rotating the Region Bounded by the Given Functions about the Given Line of Rotation
25:28
Volumes II: Volumes by Washers

51m 43s

Intro
0:00
Volumes II: Volumes by Washers
0:11
Rotating Region Bounded by y=x³ & y=x around the x-axis
0:12
Equation for Volumes by Washer
11:14
Process for Solving Volumes by Washer
13:40
Example I: Find the Volume of the Solid Obtained by Rotating the Region Bounded by the Following Functions around the Given Axis
15:58
Example II: Find the Volume of the Solid Obtained by Rotating the Region Bounded by the Following Functions around the Given Axis
25:07
Example III: Find the Volume of the Solid Obtained by Rotating the Region Bounded by the Following Functions around the Given Axis
34:20
Example IV: Find the Volume of the Solid Obtained by Rotating the Region Bounded by the Following Functions around the Given Axis
44:05
Volumes III: Solids That Are Not Solids-of-Revolution

49m 36s

Intro
0:00
Solids That Are Not Solids-of-Revolution
0:11
Cross-Section Area Review
0:12
Cross-Sections That Are Not Solids-of-Revolution
7:36
Example I: Find the Volume of a Pyramid Whose Base is a Square of Side-length S, and Whose Height is H
10:54
Example II: Find the Volume of a Solid Whose Cross-sectional Areas Perpendicular to the Base are Equilateral Triangles
20:39
Example III: Find the Volume of a Pyramid Whose Base is an Equilateral Triangle of Side-Length A, and Whose Height is H
29:27
Example IV: Find the Volume of a Solid Whose Base is Given by the Equation 16x² + 4y² = 64
36:47
Example V: Find the Volume of a Solid Whose Base is the Region Bounded by the Functions y=3-x² and the x-axis
46:13
Volumes IV: Volumes By Cylindrical Shells

50m 2s

Intro
0:00
Volumes by Cylindrical Shells
0:11
Find the Volume of the Following Region
0:12
Volumes by Cylindrical Shells: Integrating Along x
14:12
Volumes by Cylindrical Shells: Integrating Along y
14:40
Volumes by Cylindrical Shells Formulas
16:22
Example I: Using the Method of Cylindrical Shells, Find the Volume of the Solid
18:33
Example II: Using the Method of Cylindrical Shells, Find the Volume of the Solid
25:57
Example III: Using the Method of Cylindrical Shells, Find the Volume of the Solid
31:38
Example IV: Using the Method of Cylindrical Shells, Find the Volume of the Solid
38:44
Example V: Using the Method of Cylindrical Shells, Find the Volume of the Solid
44:03
The Average Value of a Function

32m 13s

Intro
0:00
The Average Value of a Function
0:07
Average Value of f(x)
0:08
What if The Domain of f(x) is Not Finite?
2:23
Let's Calculate Average Value for f(x) = x² [2,5]
4:46
Mean Value Theorem for Integrate
9:25
Example I: Find the Average Value of the Given Function Over the Given Interval
14:06
Example II: Find the Average Value of the Given Function Over the Given Interval
18:25
Example III: Find the Number A Such that the Average Value of the Function f(x) = -4x² + 8x + 4 Equals 2 Over the Interval [-1,A]
24:04
Example IV: Find the Average Density of a Rod
27:47
Section 6: Techniques of Integration
Integration by Parts

50m 32s

Intro
0:00
Integration by Parts
0:08
The Product Rule for Differentiation
0:09
Integrating Both Sides Retains the Equality
0:52
Differential Notation
2:24
Example I: ∫ x cos x dx
5:41
Example II: ∫ x² sin(2x)dx
12:01
Example III: ∫ (e^x) cos x dx
18:19
Example IV: ∫ (sin^-1) (x) dx
23:42
Example V: ∫₁⁵ (lnx)² dx
28:25
Summary
32:31
Tabular Integration
35:08
Case 1
35:52
Example: ∫x³sinx dx
36:39
Case 2
40:28
Example: ∫e^(2x) sin 3x
41:14
Trigonometric Integrals I

24m 50s

Intro
0:00
Example I: ∫ sin³ (x) dx
1:36
Example II: ∫ cos⁵(x)sin²(x)dx
4:36
Example III: ∫ sin⁴(x)dx
9:23
Summary for Evaluating Trigonometric Integrals of the Following Type: ∫ (sin^m) (x) (cos^p) (x) dx
15:59
#1: Power of sin is Odd
16:00
#2: Power of cos is Odd
16:41
#3: Powers of Both sin and cos are Odd
16:55
#4: Powers of Both sin and cos are Even
17:10
Example IV: ∫ tan⁴ (x) sec⁴ (x) dx
17:34
Example V: ∫ sec⁹(x) tan³(x) dx
20:55
Summary for Evaluating Trigonometric Integrals of the Following Type: ∫ (sec^m) (x) (tan^p) (x) dx
23:31
#1: Power of sec is Odd
23:32
#2: Power of tan is Odd
24:04
#3: Powers of sec is Odd and/or Power of tan is Even
24:18
Trigonometric Integrals II

22m 12s

Intro
0:00
Trigonometric Integrals II
0:09
Recall: ∫tanx dx
0:10
Let's Find ∫secx dx
3:23
Example I: ∫ tan⁵ (x) dx
6:23
Example II: ∫ sec⁵ (x) dx
11:41
Summary: How to Deal with Integrals of Different Types
19:04
Identities to Deal with Integrals of Different Types
19:05
Example III: ∫cos(5x)sin(9x)dx
19:57
More Example Problems for Trigonometric Integrals

17m 22s

Intro
0:00
Example I: ∫sin²(x)cos⁷(x)dx
0:14
Example II: ∫x sin²(x) dx
3:56
Example III: ∫csc⁴ (x/5)dx
8:39
Example IV: ∫( (1-tan²x)/(sec²x) ) dx
11:17
Example V: ∫ 1 / (sinx-1) dx
13:19
Integration by Partial Fractions I

55m 12s

Intro
0:00
Integration by Partial Fractions I
0:11
Recall the Idea of Finding a Common Denominator
0:12
Decomposing a Rational Function to Its Partial Fractions
4:10
2 Types of Rational Function: Improper & Proper
5:16
Improper Rational Function
7:26
Improper Rational Function
7:27
Proper Rational Function
11:16
Proper Rational Function & Partial Fractions
11:17
Linear Factors
14:04
Irreducible Quadratic Factors
15:02
Case 1: G(x) is a Product of Distinct Linear Factors
17:10
Example I: Integration by Partial Fractions
20:33
Case 2: D(x) is a Product of Linear Factors
40:58
Example II: Integration by Partial Fractions
44:41
Integration by Partial Fractions II

42m 57s

Intro
0:00
Case 3: D(x) Contains Irreducible Factors
0:09
Example I: Integration by Partial Fractions
5:19
Example II: Integration by Partial Fractions
16:22
Case 4: D(x) has Repeated Irreducible Quadratic Factors
27:30
Example III: Integration by Partial Fractions
30:19
Section 7: Differential Equations
Introduction to Differential Equations

46m 37s

Intro
0:00
Introduction to Differential Equations
0:09
Overview
0:10
Differential Equations Involving Derivatives of y(x)
2:08
Differential Equations Involving Derivatives of y(x) and Function of y(x)
3:23
Equations for an Unknown Number
6:28
What are These Differential Equations Saying?
10:30
Verifying that a Function is a Solution of the Differential Equation
13:00
Verifying that a Function is a Solution of the Differential Equation
13:01
Verify that y(x) = 4e^x + 3x² + 6x + e^π is a Solution of this Differential Equation
17:20
General Solution
22:00
Particular Solution
24:36
Initial Value Problem
27:42
Example I: Verify that a Family of Functions is a Solution of the Differential Equation
32:24
Example II: For What Values of K Does the Function Satisfy the Differential Equation
36:07
Example III: Verify the Solution and Solve the Initial Value Problem
39:47
Separation of Variables

28m 8s

Intro
0:00
Separation of Variables
0:28
Separation of Variables
0:29
Example I: Solve the Following g Initial Value Problem
8:29
Example II: Solve the Following g Initial Value Problem
13:46
Example III: Find an Equation of the Curve
18:48
Population Growth: The Standard & Logistic Equations

51m 7s

Intro
0:00
Standard Growth Model
0:30
Definition of the Standard/Natural Growth Model
0:31
Initial Conditions
8:00
The General Solution
9:16
Example I: Standard Growth Model
10:45
Logistic Growth Model
18:33
Logistic Growth Model
18:34
Solving the Initial Value Problem
25:21
What Happens When t → ∞
36:42
Example II: Solve the Following g Initial Value Problem
41:50
Relative Growth Rate
46:56
Relative Growth Rate
46:57
Relative Growth Rate Version for the Standard model
49:04
Slope Fields

24m 37s

Intro
0:00
Slope Fields
0:35
Slope Fields
0:36
Graphing the Slope Fields, Part 1
11:12
Graphing the Slope Fields, Part 2
15:37
Graphing the Slope Fields, Part 3
17:25
Steps to Solving Slope Field Problems
20:24
Example I: Draw or Generate the Slope Field of the Differential Equation y'=x cos y
22:38
Section 8: AP Practic Exam
AP Practice Exam: Section 1, Part A No Calculator

45m 29s

Intro
0:00
Exam Link
0:10
Problem #1
1:26
Problem #2
2:52
Problem #3
4:42
Problem #4
7:03
Problem #5
10:01
Problem #6
13:49
Problem #7
15:16
Problem #8
19:06
Problem #9
23:10
Problem #10
28:10
Problem #11
31:30
Problem #12
33:53
Problem #13
37:45
Problem #14
41:17
AP Practice Exam: Section 1, Part A No Calculator, cont.

41m 55s

Intro
0:00
Problem #15
0:22
Problem #16
3:10
Problem #17
5:30
Problem #18
8:03
Problem #19
9:53
Problem #20
14:51
Problem #21
17:30
Problem #22
22:12
Problem #23
25:48
Problem #24
29:57
Problem #25
33:35
Problem #26
35:57
Problem #27
37:57
Problem #28
40:04
AP Practice Exam: Section I, Part B Calculator Allowed

58m 47s

Intro
0:00
Problem #1
1:22
Problem #2
4:55
Problem #3
10:49
Problem #4
13:05
Problem #5
14:54
Problem #6
17:25
Problem #7
18:39
Problem #8
20:27
Problem #9
26:48
Problem #10
28:23
Problem #11
34:03
Problem #12
36:25
Problem #13
39:52
Problem #14
43:12
Problem #15
47:18
Problem #16
50:41
Problem #17
56:38
AP Practice Exam: Section II, Part A Calculator Allowed

25m 40s

Intro
0:00
Problem #1: Part A
1:14
Problem #1: Part B
4:46
Problem #1: Part C
8:00
Problem #2: Part A
12:24
Problem #2: Part B
16:51
Problem #2: Part C
17:17
Problem #3: Part A
18:16
Problem #3: Part B
19:54
Problem #3: Part C
21:44
Problem #3: Part D
22:57
AP Practice Exam: Section II, Part B No Calculator

31m 20s

Intro
0:00
Problem #4: Part A
1:35
Problem #4: Part B
5:54
Problem #4: Part C
8:50
Problem #4: Part D
9:40
Problem #5: Part A
11:26
Problem #5: Part B
13:11
Problem #5: Part C
15:07
Problem #5: Part D
19:57
Problem #6: Part A
22:01
Problem #6: Part B
25:34
Problem #6: Part C
28:54
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Volumes II: Volumes by Washers

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Volumes II: Volumes by Washers 0:11
    • Rotating Region Bounded by y=x³ & y=x around the x-axis
    • Equation for Volumes by Washer
    • Process for Solving Volumes by Washer
  • Example I: Find the Volume of the Solid Obtained by Rotating the Region Bounded by the Following Functions around the Given Axis 15:58
  • Example II: Find the Volume of the Solid Obtained by Rotating the Region Bounded by the Following Functions around the Given Axis 25:07
  • Example III: Find the Volume of the Solid Obtained by Rotating the Region Bounded by the Following Functions around the Given Axis 34:20
  • Example IV: Find the Volume of the Solid Obtained by Rotating the Region Bounded by the Following Functions around the Given Axis 44:05

Transcription: Volumes II: Volumes by Washers

Hello, welcome back to www.educator.com, and welcome back to AP Calculus.0000

Today, we are going to talk about taking volumes of solids by the method of washers.0004

Let us jump right on in.0011

In the last lesson, we introduced this notion of taking a function, rotating that function around a certain axis.0013

Generating a solid, a solid of revolution, and then taking slices.0020

And then, taking the cross sectional area, finding that little differential volume.0024

And then, integrating, adding up all of those volumes.0030

Now let us continue that, let me go ahead and work in blue here.0033

Sometimes when we rotate a region around a given axis, we do not get a complete solid of revolution.0039

In other words, we do not get a full… Like if I take a cup and fill it full of water, that whole cup full of water is a solid.0085

Sometimes there are some hollows, there are things that are not quite complete.0094

Let us take a look at an example, I think it will make this clear.0098

We have the region bounded by the functions y = x³ and y = x.0103

What we are going to do is we are going to rotate this region that is bounded by those two curves around the x axis.0116

Let us see what kind of solid we get.0132

Our question is what is the volume of the resulting solid?0136

Let us go ahead and draw.0153

We have the y = x³ is going to look something like that.0158

The y = x line is going to look something like this.0162

This is our y = x, this is our y = x³, and the region that we are concerned about is this region right here, the one that bounds those.0166

This, we are going to rotate around the x axis.0175

We are going to spin it this way.0179

The thing that we actually end up generating is the following.0181

I’m going to make the axis just a little bit higher.0191

The solid that we ended up generating is going to be the following.0194

It is going to have this one, it is going to be this way.0198

This is a rough drawing.0205

There is this solid, notice this is not a complete solid, this is a hollow inside.0207

What we have done is take this region, spit it out, generate this.0217

If I were to take this thing and turn it a little bit this way, you would see something like that.0223

This is all hollow, this sort of triangular part, it is the other volume.0232

How are we going to do this, how are we going to find this volume?0237

This is how we do it, let us go ahead and draw another picture of it to make it a little bit smaller.0242

Once again, we have our region that looks something like this.0250

I will go ahead and draw this, something like that.0255

Again, we do the same thing, we are still going to slice.0261

Around the axis that we rotate, we are going to take a slice perpendicular to that axis.0266

We are going to take a little bit of a slice, it is going to look like this.0272

The slice is not going to be a single piece.0277

It is going to be a single piece, in a sense that it is one slice.0280

Again, there is this little gap right in between here.0285

I take this slice and I’m going to rotate it out, and see what it is that I look.0288

It is going look like a washer, instead of a solid disk, it is just going to be a disk with a hole in it, what we call a washer.0293

Let us go ahead and go out here.0301

This is going to be an outer disk, it is going to be that one.0309

This right here, it is going to occupy an inner circle.0313

That is what you get when you splice it.0323

When you turn it, you are going to actually get a washer.0325

This is a washer of thickness dx.0335

This is the thickness from here to here.0344

That is the thickness of that washer, that is the dx.0347

What we are going to be doing is we are going to be integrating along the x axis.0349

In other words, we are going to be integrating along the axis of rotation, along the x axis.0354

Exactly the same as before, the only thing that is different now is we want the area of this disk.0363

The area of the disk is the area the outer circle - the area of the inner circle.0368

Because the area that we are looking for is that one.0372

We are going to multiply by its thickness which is dx.0379

That is going to give us a differential volume element.0387

And then, we are going to add all of the volumes, all of the washers along the x axis.0389

Our differential volume element is nothing more than the area of this × dx.0396

The area of this is π × the outside radius² - π × the inside radius².0402

This is the outside radius, this is the inside radius × dx which is the thickness of the washer.0413

That is the volume of that washer, we want to add them all up.0422

Let me we write this, dv = π × just pull out the π, outside radius² - inside radius² dx.0426

When we integrate both sides, the integral of dv is going to be just v.0438

The volume = the integral from a to b of π × the outside radius² - the inside radius² dx.0442

That is the general formula for finding the volume of a solid,0455

that has gotten a solid of revolution generated by rotating a particular region around a given axis.0462

When that particular slice that you took is a washer, it is not quite complete.0468

It is this solid disk but it is a disk with a hole in it.0473

In this particular case, we have this function which is y = x.0477

This function y = x³, and of course, this is the x axis, that is the axis of rotation.0483

What are a and b?0493

The lower and upper limits of integration, they are just going to be just0499

from here we are integrating along the x axis to here.0502

These two graphs, we know that they meet at 1.0508

a is equal to 0 and b is equal to 1.0512

Let us go ahead and fill this in.0516

We have the volume = the integral from 0 to 1 of π × the outside radius.0519

The outside radius is this one, it is from 0 to x, it is the y value.0528

However far we go along the x axis, it is the y value.0537

It is just going to be x, the outside radius is x and we square it.0541

The inside radius, it is just this point right here.0547

We go along x and it goes up to the x³ part.0551

This is going to be x³² dx.0557

That is going to equal π × the integral from 0 to 1 of x² - x⁶ dx.0565

This is really what we want.0575

The most important thing in all of these problems is actually finding the integral, establishing the integral.0577

Solving it is important but it is the secondary concern.0583

We need to take a situation, convert it into an integral.0587

My students, when I teach this course, I generally have them stop here.0591

I do not want them to solve the integral.0596

This is what I'm interested in, I'm interested that they actually can form the integral.0597

The rest is just techniques of integration, or software, if you need.0602

Let us go ahead and solve this though.0608

The volume is equal to π × this is going to be x³/ 3 – x⁷/ 7 from 0 to 1.0610

The final answer is 1/3 - 1/7, that is it.0625

That is all we are doing here.0634

Same exact thing that we did before, except now we are just looking for the cross sectional area0635

which happens to be outer circle - inner circle, because we are dealing with a washer.0640

All of these problems are dealt with the same way, in some form or another.0646

That is all we are doing.0650

We are finding some area, we are multiplying it by a differential length dx.0651

That is our differential volume.0656

We are going to add up all those volumes, that is all it is.0657

We just need to make sure that we see what is happening pictorially.0660

That is going to be the hardest part in all of these problems.0664

What is it look like, how does one visualize this?0666

Let us go ahead and, a little bit further before we start our examples.0672

When you are faced with a region that generate washers upon slicing,0679

the volume is equal to the integral from a to b of π × the outside radius² - the inside radius² dx.0706

If you are going to be integrating along the dy, then this is just outside radius - inside radius dy.0725

The problem itself will tell you whether you are generating along x or generating along y.0733

I will do this in red, this really is the most important part about all of these things.0741

Not just this particular section but all of these, generating volumes and things like that.0746

The most important thing you always measure the radii or any length for that matter from the axis of rotation.0753

Whatever the axis of rotation is, x = 5, y = -1, it is from that point that you are measuring.0781

From there, the distance from that to the particular functions that we are dealing with.0788

This is the generic, once you have a picture, you are going to decide what our outside is, what our inside is.0795

Again, you always measure radii from the axis of rotation.0802

Let me go back to blue.0807

Examples will make this clear.0809

Our general process, number 1, always draw a picture.0822

Two, identify your solid, identify the solid.0833

In other words, once you actually perform the rotation, make sure you have an idea of what the solid looks like.0838

It does not have to be a 100% full graph but you should at least be able to see this side view, what it actually looks like.0845

Three, identify the washer.0854

In other words, take a slice, draw it out, identify the washer.0861

This identification of the washer, whether it is this way or this way,0869

this will decide whether you are integrating with respect to x or y.0875

Instead of saying with respect to, integrating along x or y.0901

The final part, number 4, measure radii from the axis of rotation to the original graph.0910

Once you generate your solid, you are going to have that other half.0940

From the axis of rotation, measure to the original graph, that is going to give you your length.0945

Again, it will make more sense when we start our example problems.0949

With that, let us go ahead and start our example problems here.0953

Find the volume of the solid obtained by rotating the region bounded by the following functions around the given axis.0959

We have the function y = x³, y = x, x greater than or equal to 0.0967

We want you to rotate it around y = 3.0972

Same functions as before, different axis of rotation.0976

Let us draw this out, see what it looks like.0982

Let us go down here.0987

We are rotating this around y = 3.1000

I’m going to go this way, there we go.1003

y = x is that line, y = x³ is going to be that thing.1008

What we are going to do is going to rotate it around this line.1024

This is our y = 3 line.1034

When we rotate that way, now what we are going to do is we are going to get something that looks, it is going to be over here.1036

Let me extend this out, it is not a problem.1046

We are going to get something like that.1050

We are going to rotate that way.1052

What we are interested in is this region right here.1054

That solid, whatever it is, is going to have a volume.1059

We want to find that volume.1063

We draw our region, let me see, 1, process, we drew our region.1069

Two, we identify the solid.1079

Three, we identify the washer.1085

We are going to take a slice of this, we are not going to go this way, nothing there.1093

Let me go to red actually.1099

We are going to slice it this way.1102

We are just going to take a slice that way.1107

When we take this and turn it around, what we are going to end up getting is right over here.1109

Our view is slightly to the side, not fully turned so you see it this way.1121

But just a little bit so you can see what is actually going on.1125

Here is this washer of a given thickness.1130

The region that we are interested in is that region right there.1141

There we go, we know the washer is a vertical washer.1146

We are going to be adding all of the washers this way.1150

We are going to be integrating along the x axis, integrate in the x direction.1152

We will just say integrate along x.1167

This is going to be from 0 to 1 again, because from 0 and 1.1170

From here, we are going to integrate that way.1176

We are going to integrate that way, along the axis.1178

Part 4, measure the radii from the axis of rotation to the original graph.1185

Outside radius, inside radius, outside radius, inside radius.1204

Let me go back to blue here.1211

Let me go to black.1213

Outside radius is that radius.1215

Inside radius is that radius.1220

We said to measure the radii to the original graph.1227

The original graph is here.1231

Let me erase that.1233

That is our outside radius, that is our inside radius.1245

Measure it to the original graph because that is actually where the function is.1253

The function is here.1258

Our outside radius, distance is what we are worried about.1260

This distance is 3, this distance here is x³, because if this is x, this height here is x³.1267

Our outside radius is 3 - x³.1280

The whole distance - this little distance, that gives me this distance.1285

The inside radius, it is the whole distance 3 - this distance, from here to here that is x.1292

Now that we have our outside and inside radius, the rest is really simple.1304

We just have volume = the integral, let me write the formula one more time.1309

a to b π × the outside radius² - the inside radius² dx.1318

It is always a nice idea to write the equation over and over again.1326

That is a way of memorizing it, before you start the problem.1330

In this case, it is going to be the integral from 0 to 1 of π × outside radius 3 - x³² - inside radius 3 - x² dx.1333

That is the integral that we want to solve.1354

Volume = π × integral from 0 to 1.1358

In other words, this is technically where you can stop.1364

You have converted the problem to the integral.1370

Now it is just an integration problem.1372

0 to 1, we got 9 – 6x³ + x⁶ - 9 - 6x + x², all of that dx.1375

9 – 9, the - - this function².1411

The minus is going to distribute over everything.1418

We are going to get = π × integral from 0 to 1.1424

We are left with -6 x³ + x⁶ + 6x - x² dx,1445

is equal to the π × -6x⁴/ 4 + x⁷/ 7 + 6x²/ 2 - x³/ 3 evaluated from 0 to 1.1461

When I add it all together, I get 1.31 π.1481

If I have done my arithmetic correctly, which is always a tossup.1485

In any case, that is it, getting the integral is the most important part.1491

Changing the actual problem itself, the physical thing that we are looking at, into some sort of integral.1496

The rest is integration.1505

Let us take a look at example 2, find the volume of a solid obtained by rotating the region1510

bounded by the following functions around the given axis.1513

Again, we have y = x³, this time we have y = √x, x is greater than or equal to 0.1517

We want to rotate this around x = 2.1524

Let us go ahead and draw our region.1528

I probably do not want to make it quite so big.1537

Let me spare myself a little bit of room here.1539

I have got y = x³, it is going to be like that.1546

y = √x, it is going to look like that.1550

They happen to meet at 1.1554

Basically, y = x³ is going to go off that way.1556

y = √x is going to go off that way.1560

They are going to meet here.1562

The region that I'm interested in is this region right here.1564

Of course, x is greater than or equal to 0, I’m interested in this region.1567

I’m rotating it around x = 2.1572

If this is 1, this is 2, I’m rotating it that way which means I'm going to have that and I’m going to have that.1575

This is the region than I'm interested in, this thing.1594

I’m looking at it straight on, that is my solid.1604

Draw the region, we have drawn the region.1611

Identify the solid, we have identified the solid.1616

Region is this way, rotating around this axis.1628

The slice that we take is going to be perpendicular to the axis.1633

If you are ever not sure how you are going to slice, you are going to slice perpendicular to the axis.1637

This direction is not perpendicular to the axis.1643

This direction is perpendicular the axis.1647

Our washer is going to be, that is a characteristic washer.1650

Since that is a characteristic washer, we are going to be adding washers in the vertical direction from 0 to 1.1661

This is 0, this is 1.1669

Our lower and upper limit of integration are 0 and 1.1672

We are integrating along the y axis.1675

When we are integrating along the y axis, we need functions of y.1679

Identify the washer which means we integrate along y.1683

You know what, I think I should probably write up my words a little bit better than this.1696

Let us go ahead and identify our outside radius and our inside radius.1710

Let us integrate along y and we are going to be going from 0 to 1.1719

We know that the volume is equal to the integral from a to b of π × the outside radius² - the inside radius² dy.1727

That is going to be our general equation.1740

dy, we need functions of y not functions of x.1742

We express these functions, that function, and that function.1751

We express these functions as functions of y.1764

y = x³ that is going to become x = y¹/3.1774

y = √x that is going to turn into x = y².1785

These are the functions that I’m going to be dealing with.1794

I’m integrating along y which means my formula is going to have a dy.1800

The differential is in the y direction.1806

Therefore, my functions have to be in terms of y, that is what is going on.1808

Let us go ahead and find our outside and inside radius.1813

Outside radius is, we measure from the axis of rotation to the original function which is this one right here.1816

Our outside radius is that one.1825

Our inside radius is this one.1831

Our outside radius is 2.1835

This distance 2 - the distance from here to here.1840

The distance from here to here is this, it is y².1844

This x distance, whatever y is, our distance is y², that is the whole idea.1849

We have 2 - y² is our outside radius.1855

Our inside radius is the distance, it is from here to here.1860

This distance is from here to here which is 2 - this distance which is the y¹/3, 2 – y¹/3.1864

There we go, now we have got it.1878

Our volume is equal to the integral from 0 to 1 of π × the outside radius1885

which is 2 - y²² - the inside radius which is 2 – y¹/3² dy.1893

That is the most important part, coming up with this integral.1908

The rest is just integration.1911

We have got π × the integral from 0 to 1.1914

Let us go ahead and multiply all of these out.1919

We have got 4 - 4y² + y⁴ - 2 × 2 is 4 - 4 × y¹/3 + y²/3 dy.1921

Our 4’s go away, the negative sign distributes.1946

I have not done the integral yet, be very careful.1954

The integral from 0 to 1 of -4y² + y⁴ + 4y¹/3 – y²/3, all of that dy.1958

In your AP exam as you know, there are going to be some sections where you are going to have to do the integration by hand.1981

There are going to be some sections where you are going to do the integration,1986

where you are going to be allowed to use your calculator.1989

In this particular case, it depends.1992

Sometimes, it is nice to use a calculator.1995

Sometimes, it is nice to do it by hand.1996

You will have both options.1998

The idea is to be able to integrate this by hand, if you need to.2000

But again, on the calculator section you are just going to be plugging this in and getting an answer.2004

You are not going to be doing the integration like we are doing here.2009

We have got π × this is going to be -4y³/ 3.2014

This is going to be + y⁵/ 5.2023

This is going to be + 4y⁴/3 / 4/3 - y⁵/3 / 5/3.2026

Again, it is just my particular habit of not simplifying these and making this 3y⁵/3/ 5.2032

It is up to you, the rest is just arithmetic.2048

I ended up with 1.27 π, when I actually put this into my calculator.2051

Let us try our third example.2061

Find the volume of a solid obtained by rotating the region bounded by the following functions around the given axis.2064

We have y = 2 sin x, y = 2 cos x.2069

The x from π/4 to 5π/ 4.2073

We want to rotate this around y = -3.2076

Let us see what the heck is going to be going on here.2082

Let me work in blue for my graph.2086

I will go this way.2100

This is my x and y axis.2101

y = 2 sin x, it is a normal sin function, except the height is 2.2104

Down here this is -2.2116

Cos function starts here, it passes here, here, here, and here.2121

The cos function looks like this.2132

Not the best drawing in the world but I think we understand what is happening.2138

π/4 to 5π/ 4, that is this point and this point.2143

Our integration, if we decide to go along the x axis, it is probably going to be from π/4 to 5π/ 4.2148

Let us generate the solid and see what we have.2157

We have taken care of this.2160

Let us rotate around the line y = -3.2161

y = -3, let us go ahead and put it like right there.2164

This is -3, we are going to rotate this region right here around this axis right here.2168

Let us see what we get.2182

We end up with something that looks like this.2183

Again, I do not promise the best graph but here is something.2189

Something like that.2194

We have this nice region, this thing that we have rotated around there, rotated around there.2196

We have this solid of revolution.2206

Now we are going to take a slice.2210

We take a slice perpendicular to the axis of rotation.2212

The axis of rotation of this way, we are going to slice it this way.2216

Our slice is going to be vertical.2220

Our washer is that.2223

When I take this, rotated it out a little bit like that, what you are going to get is a side view of your washer.2232

That is your washer.2245

It is going to have a certain thickness, that is going to be our dx.2247

In this particular case, we are going to be integrating along the x axis.2252

We are going to integrate along the x axis and we are going to go from π/4 to 5π/ 4.2258

Lower and upper limit of integration, respectively.2268

A little bit of an issue here with sins and cos and other functions that tend to occupy both above the axis and below the axis.2275

We said we are going to measure our radius.2284

We are going to have an outside radius.2287

We are going to have an inside radius.2289

Let me go to black, our outside radius, we are going to measure from the axis of rotation to the original function.2294

Our outside radius is that one.2301

Our inside radius is this one.2305

Distance, what is this distance?2311

It is the distance from here to here which is 3, because from -3 to 0 is 3, + this distance here.2315

That is the function, that is the 2 sin x function.2326

Our outside radius is going to be 3 + 2 sin x.2332

Now inside radius, this is where it gets a little interesting.2341

Again, it is going to be this distance 3 - this distance.2344

3, it is actually going to be +, here is why.2355

Wherever you are from π/4 to 5π/ 4, the cos is going to take on positive values and it is going to take on negative values.2360

The function itself accounts for the negative sin here.2371

Because sometimes it is going to be this + that, sometimes it is going to be this – that.2376

The function itself accounts for it.2386

It is just 3 + 2 cos x.2388

In this particular case, this particular slice, the cos x function is below the axis.2393

It is going to be 3 - 2 cos x.2398

I will leave it as + because the 2 cos x is going to be negative itself.2404

It is going to be 3 – a number.2408

I hope that make sense.2411

There we go, we have our outside radius, we have our inside radius.2414

Now our volume is really simple.2417

Our volume is going to be the integral from π/4 to 5π/ 4.2420

We are going to integrate from π/4 to 5π/ 4.2427

It is going to be π × outside radius 3 + 2 sin x² - the inside radius which is 3 + 2 cos x².2434

We are integrating along x.2459

This is the integral that we want.2463

Sometimes that will be enough.2468

Let us actually integrate it.2471

We have volume = π × the integral from π/4 to 5 π/4 of 9 + 12 sin x2474

+ 4 sin² x - 9 + 12 cos x + 4 cos² x dx.2495

This is going to equal, the 9’s cancel, I always have a thing with 0, I do not know where it is.2512

π/4 to 5π/ 4 of 12 sin x + 4 sin² x - 12 cos x - 4 cos² x.2523

There we go, this is dx.2547

This one, I just decided to go ahead and use a calculator to solve this, as opposed to doing the actual integration.2554

Part of the reason is, we can handle this one and this one, we have already learned techniques for that.2564

But in the lessons that follow, we are going to be discussing techniques of integration2570

for other types of functions that we have to integrate.2575

One of them is going to be the sin² function and the cos² function.2580

Technically, as far as the progress of this course is concerned, we have not learned how to deal with these integrals formally.2583

Just go ahead and use your calculator, in this case.2591

But make sure that your calculator is in radian mode.2594

Otherwise, you will get the wrong answer.2602

Make sure your calculator is in radian mode, when you do any of the integrals.2604

Definitely check that before you go in the AP exam or any other exam,2613

when you are doing these and you are going to be using your calculator, radian mode.2616

Everything is in radian mode in calculus.2620

When I actually plug this in and do the integral, I get a volume equal to 33.94.2627

Again, finding the integral is the important part.2637

Let us do one more example.2640

Find the volume of a solid obtained by rotating the region around the given axis.2647

This time we have x² + y² = 9.2651

We are given an equation in implicit form not explicitly.2654

x is greater than 0, y is greater than 0, rotate around x = 3.2658

We have to decide what we are going to do.2661

Let us go ahead and turn this into an equation that we actually recognize.2666

This is going to be x²/ 3² + y²/ 1² = 1.2669

This is the equation of an ellipse.2681

We are going to take the x is greater than or equal to 0 and the y greater than or equal to 0.2687

What we are looking at is here.2691

What we are looking at is an ellipse.2697

The x direction, we are going to go 1, 2, 3.2702

y direction we are going to go 1.2705

But we want only the region that is above the x, axis above the y axis.2708

It is just this, region right here.2716

It continues on this way but the region that we are interested in is this region right here.2719

They say rotate around x = 3.2727

That is this axis right here.2730

When we rotate around that axis, we are going to end up getting that region.2734

We are going to take a slice of that region.2748

We are going to take a slice perpendicular to the axis of rotation.2749

The axis of rotation is vertical, the slice we are going to take is horizontal.2752

Our representative washer, when we slice this solid, our solid is this.2757

When we take a slice of it, we are going to end up getting a washer.2767

When I take that washer and turn it this way, it is going to look exactly like you think it is going to look.2771

It is going to look like this.2777

It looks like that.2782

It is going to have a thickness which is going to be dy.2783

When we add up all these washers, we are adding them vertically.2789

We are going to be integrating along the y axis.2791

We are going to be integrating from 0 to 1, nice perfect.2801

So far so good, now we are integrating along y.2809

We need to express these functions as functions of y.2813

We are going to turn this into a function of y.2815

Let me just write that out.2831

Integrating along y means expressing functions as functions of y.2833

Now I have got x² + 9y² = 9.2853

I have got x² = 9 – 9y².2860

I have x = √9 - 9y².2866

Do not worry about simplification, just leave it as is.2873

Pulling out 9 and 3, it is not even worth it.2876

Let us go ahead and talk about our inside radius and our outside radius.2880

Let us talk about our outside radius first.2884

I will go to black.2886

We are going to measure from the axis of rotation to the original function.2887

The outside radius is that one, the inside radius is this one.2894

The outside radius is just 3.2904

Nice because it stays always 3.2908

The inside radius that is the radius that is going to be short or long.2914

That is the one that changes.2919

Inside radius, it is going to be 3.2921

It is going to be this distance - this distance because we want this distance right here.2925

This whole thing - this thing.2934

This thing is that.2937

It is 3 - √9 - 9y².2940

There you go, now that we have that, very simple.2949

We have our volume is equal to the integral from 0 to 1 of π × the outside radius2953

which is 3² - the inside radius 3 - √9 - 9y²² dy.2963

This is the integral that we were looking for.2982

Let us go ahead and see if we can solve this.2988

We have volume is equal to π × the integral from 0 to 1 of 9 - 9 -2992

6 × 9 - √9y² + 9 - 9y² dy, which is equal to π × the integral from 0 to 1.3006

This 9 and this 9 cancel, negative sign becomes 6 × √9 - 9y², this becomes -9 and this becomes +9y² dy.3026

I just go ahead and plug this into my calculator.3046

I get myself 8.14, that is my volume.3049

Once again, you should note that some of these integrals, you have not learned how to deal with yet.3058

Do not worry about it, that is absolutely fine.3075

Some of these integrals, you have not dealt with formally.3078

We have not dealt with formally.3085

We will, very soon.3087

That is it, that is volumes by the method of washers.3097

Thank you so much for joining us here at www.educator.com.3100

We will see you next time, bye.3102

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