Question

$\angle ACD$ is an exterior angles of $△ABC$ .The measures of $A$ and $B$ are equal .If $m\left(\angle ACD\right)={140}^{\circ }$ ,find the measures of the angles $A$ and $B$

Answer 1

An exterior angle of a triangle is equal to the sum of opposite interior angles.

$\therefore ,\angle ACD=\angle A+\angle B$

$\Rightarrow 140=2\times \angle A$ since the measures of $\angle A$ and $\angle B$ are equal

$\therefore \angle A=\angle B={70}^{\circ }$