Question

$\angle ACD$ is an exterior angle of $\Delta ABC$ the measure of $\angle A$ and $\angle B$ are equal. If $\angle ACD={140}^{\circ }$, find the measure of the angles $\angle A$ and $\angle B$

Answer 1

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

Hence, In this case $\angle A$ and $\angle B$

So,

$\angle A+\angle B={140}^{\circ }$

as $\angle A=\angle B$

or,$2\angle A={140}^{\circ }$

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