A circle has a diameter AB. A point C is on the circumference. If ∠CAB=40°, what is the measure of ∠ABC?
Show answer & explanation
Correct answer: B
Explanation
Given:
AB is the diameter of the circle.
∠CAB = 40°
Formula:
Angle subtended by the diameter at the circumference = 90°
∠ACB = 90°
∠CAB + ∠ABC + ∠ACB = 180°
40° + ∠ABC + 90° = 180°
∠ABC = 180° − 130°
∠ABC = 50°