Question

∠ACD is an exterior angle of ∆ABC. ∠A and ∠B are equal. If m∠ACD = 140°, find the measures of ∠A and ∠B.

Answer 1

Given that exterior angle, ∠ACD = 140°.
Also, the measures of ∠A and ∠B are equal.

Let the measure of ∠A = x°.
So, measure of ∠B = x°.
Using exterior angle property,
m∠ACD = m∠A + m∠B
140 = x° + x°
140 = 2
$x=\frac{140°}{2}$
⇒ x = 70°
Thus, ∠A and ∠B are 70° each.