Question 12 Marks
∠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
View full question & answer→Let the measures of ∠A be x°.
m∠A = m∠B = x°
∠ACD is the exterior angle of ∆ABC
∴ m∠ACD = m∠A + m∠B
∴ 140 = x + x
∴ 140 = 2x
∴ 2x = 140
\therefore x=\frac{140}{2}
= 70
∴ The measures of the angles ∠A and ∠B is 70° each.
m∠A = m∠B = x°
∠ACD is the exterior angle of ∆ABC
∴ m∠ACD = m∠A + m∠B
∴ 140 = x + x
∴ 140 = 2x
∴ 2x = 140
\therefore x=\frac{140}{2}
= 70
∴ The measures of the angles ∠A and ∠B is 70° each.




