24. The circle shown below has diameter AD and points B and C lie on the circle. The measure of ∠CAD is 30°，and the measure of minor arc is 60°. What is the measure of minor arc ？

Answer and Explanation

Your Answer is

Correct Answer is J

Explanation

The angle of the inferior arc AC is the angle of its corresponding central angle. Because the angle corresponding to the center angle is twice the angle of the circumference angle, only the angle of ∠ADC is required. Since AD ​​is a diameter, ∠ACD=90°. And because ∠DAC=30°, so ∠ADC=60°. Therefore, the central angle is 120°.