Question

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

Answer 1

∠A + ∠B = ∠ACD (Exterior angle property)
⇒ 2∠A = 140^∘ (∵∠A = ∠B)
⇒ ∠A = 70^∘
Hence, the measures of ∠A and ∠B are 70^∘ and 70^∘ respectively.