Question

In the following figure ABCD is a trapezium in which $AB\parallel DC$. Find the measure of $\angle C$.

Answer 1

Given:

It is given that ABCD is a trapezium.
$AB\parallel DC$.
$\therefore \angle C+\angle B={180}^{\circ }\left[\text{Sum~ of ~co~interior~ angles ~is}{180}^{\circ }\right]$
$\Rightarrow \angle C+{120}^{\circ }={180}^{\circ }$
$\Rightarrow \angle C={180}^{\circ }-{120}^{\circ }\therefore \angle C={60}^{\circ }$