Question

In cyclic quadrilateral ABCD m∠A = 100°, then find m∠C.

Answer 1

Given: m∠A = 100°

In a cyclic quadrilateral, the sum of the measures of the opposite angles is always 180°. 

This property states:

m∠A + m∠C = 180° ...(Opposite angles of a cyclic quadrilateral)

100° + m∠C = 180°

m∠C = 180° − 100°

m∠C = 80°

Thus, the measure of m∠C is 80°.