Section 10 – 2

Find Arc Measures

VocabularyCentral Angle – An angle whose vertex is the center of the circle.Minor Arc – An arc whose measurement is less than 180°.

Major Arc – An arc whose measurement is greater than 180°.

is a central angle of

ACB

VocabularySemicircle – An arc with endpoints of a diameter and whose measurement is 180°.

is a semicircle.BDE

VocabularyMeasure of Whole Circle is: 360°

Measure of Semicircle is: 180°

Measure of Minor Arc is the measure of the CENTRAL ANGLE!

Measure of Major Arc is the difference between 360° and the CENTRAL ANGLE!

Arc Addition Postulate (Post 23)

The measure of an arc formed by two adjacent arcs is the sum of the measures of the two arcs.

Example 1

Example 2

Example 3

HomeworkSection 10-2

Page 661 – 663 1, 3 – 14,

17, 22 – 24,29 – 34