1. Warm up 1. Solve for x: 120o xo 2. Solve for each missing measure: aoco bo
98o

2. (6.2) Finding Arc Measures

3. An Angle whose vertex is at the center of the circle
Central Angle :
An Angle whose vertex is at the center of the circle A
Major Arc
Minor Arc
More than 180°
Less than 180°
ACB P AB
To name: use 3 letters C
To name: use 2 letters B
APB is a Central Angle

4. An Arc that equals 180° is called a
EDF?
What is the measure of
180˚ P E F D
An Arc that equals 180° is called a
SEMICIRCLE
To name: Use 3 letters

5. D E A B F Minor Arc Semicircle Minor Arc What is arc AF?
What is arc BEA?
What is arc ED? E A
Minor Arc
Semicircle B F
Minor Arc

6. THINGS TO KNOW AND REMEMBER ALWAYS
A circle has 360 degrees
A semicircle has 180 degrees
Vertical Angles are Equal

7. measure of an arc = measure of central angle96 Q
m AB =
96° B C
m ACB =
264°
HINT: How many degrees is in a circle?
m AE =
84°
HINT: How many degrees is in a semicircle?

8. Arc Addition PostulateB
m ABC =
m AB
+ m BC

9. D E A B F 86˚ 124˚ 180˚ 38˚ What is the measure of arc AF?
What is the measure of angle of DEB?
What is the measure of arc BEA?
What is the measure of arc ED? E
86˚ A
38º
56º
86º
86º
124˚
94º B F
180˚
38˚

10. Find the missing measures:
140˚ D A R 40
100˚ 80 C
220˚ B

11. In the same circle, or in congruent circles, two minor arcs are congruent if and only if their corresponding chords are congruent. B C
AB  CD IFF AB  DC A D

12. What is x? 60
120
120 x
x = 60

13. What is x? 2x
x + 40
2x = x + 40
x = 40