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### Angles and Arc

• Central angle: An angle whose vertex is at the center of a circle
• The sum of the measures of the central angles of a circle all adjacent to each other is 360 degrees
• Know the difference between a minor and major arc
• Arc measure: The measure of a minor arc is the measure of its central angle. The measure of a major arc is 360 degrees minus the measure of its central angle
• The measure of a semicircle is 180 degrees
• Arc Addition Postulate: The measures of an arc formed by two adjacent arcs is the sum of the measures of the two arcs
• Arc Length: A part of the circumference proportional to the measure of the arc compared to the entire circle
• Concentric Circles: Circles that lie in the same plane with the same center, but have different radii
• Concentric circles, along with all other circles, are similar
• Circles that have the same radii are congruent
• Congruent circles are also similar circles
• Two arcs of one circle with the same measure are congruent arcs
• Congruent arcs also have the same arc length

## Angles and Arc

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