Enter your Sign-on user name and password.

Forgot password?
  • Follow us on:
Loading video...

Start Learning Now

Our free lessons will get you started (Flash® 10 required).
Get immediate access to our entire library.

Sign up for Educator.com

Features Overview

  • Get on-demand access to our complete library
  • Search and jump to exactly what you need to learn
  • Track your progress
  • Download practice and lesson files
  • *Ask questions and get answers from our community & instructors

Proving Angle Relationships

  • Supplement Theorem: If two angles form a linear pair, then they are supplementary angles
  • Congruence of Angles: Congruence of angles is reflexive, symmetric, and transitive
  • Angle Theorems:
    • Angles supplementary to the same angle or to congruent angles are congruent
    • Angles complementary to the same angle or to congruent angles are congruent
    • All right angles are congruent
    • Vertical angles are congruent
    • Perpendicular lines intersect to form four right angles

Proving Angle Relationships

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.

Mathematics: Geometry