Mathematics for IGCSE & O level - Circle Theorems (Section 3 - No. 6)
In a cyclic quadrilateral ABCD, angle A is 80 degrees. What is the measure of angle C?
80 degrees
90 degrees
100 degrees
120 degrees
解释
Opposite angles in a cyclic quadrilateral are supplementary. Angle C = 180 - Angle A = 180 - 80 = 100.