Question

In a parallelogram $ABCD$, determine the sum of $\angle C$ and $\angle D$.

Answer 1

It is known that the sum of any two adjacent angles of a parallelogram is ${180}^o$

In parallelogram $ABCD$, $\angle C$ and $\angle D$ are adjacent angles.

$\Rightarrow$ The sum of $\angle C$ and $\angle D$ is ${180}^o.$