Question #N567
The points A, B, and C lie on a circle with center O. The measure of angle AOB is 120 degrees. What is the measure of angle ACB?
A. 30
B. 60
C. 90
D. 120
Correct Answer is: B
Angle ACB intercepts arc AB, and angle AOB is the central angle intercepting arc AB. The measure of an inscribed angle is half the measure of its intercepted arc, so the measure of angle ACB is half the measure of angle AOB. Therefore, the measure of angle ACB is 60 degrees.