In quadrilateral $PQRS$,$PQ = PS$ and $RQ = RS$. Prove that $\angle PQR = \angle PSR$.

(N/A) $1$. Consider the two triangles $\triangle PQR$ and $\triangle PSR$.
$2$. In these triangles,we are given that $PQ = PS$ (Side).
$3$. We are also given that $RQ = RS$ (Side).
$4$. The side $PR$ is common to both triangles,so $PR = PR$ (Side).
$5$. By the $SSS$ (Side-Side-Side) congruence criterion,$\triangle PQR \cong \triangle PSR$.
$6$. Since the triangles are congruent,their corresponding parts are equal ($CPCT$ - Corresponding Parts of Congruent Triangles).
$7$. Therefore,$\angle PQR = \angle PSR$.