From the given figure, find m∠CBD.

Question

A. 155

B. 125

C. 55

D. 70

Answer 1

Because it is an isosceles triangle, the two base angles A and B are equal. Let the measure of angles A and B be x, then since the sum of the angles of a triangle are 180 and angle C = 70, the x + x + 70 = 180 and x = 55, so m<B and m<A = 55.

<CBD is an exterior angle, whose measure is equal to the sum of the two non-adjacent interior angles, <A and <C, so m<CBD = 55 + 70 = 125 (B).