Question

Question 146
In parallelogram ABCD, find $\angle B,\angle C$ and $\angle D$.

Answer 1

In a parallelogram, the opposite angles are equal, therefore $\angle C=\angle A={80}^{\circ }$.
Also, adjacent angles are supplementary.
$\therefore \angle A+\angle B={180}^{\circ }{80}^{\circ }+\angle B={180}^{\circ }\angle B={180}^{\circ }-{80}^{\circ }\Rightarrow \angle B={100}^{\circ }$
Now, $\angle B=\angle D$ [Opposite angles are equal]
$\therefore \angle D={100}^{\circ }$.