Two tangents $PQ$ and $PR$ are drawn from an external point $P$ to a circle with centre $O$. Prove that $QORP$ is a cyclic quadrilateral.

(N/A) Given: Two tangents $PQ$ and $PR$ are drawn from an external point $P$ to a circle with centre $O$.
To prove: $QORP$ is a cyclic quadrilateral.
Proof:
$1$. Since $PQ$ and $PR$ are tangents to the circle at points $Q$ and $R$ respectively,the radius is perpendicular to the tangent at the point of contact.
$2$. Therefore,$OQ \perp PQ$ and $OR \perp PR$.
$3$. This implies $\angle OQP = 90^{\circ}$ and $\angle ORP = 90^{\circ}$.
$4$. In quadrilateral $QORP$,the sum of the opposite angles is $\angle OQP + \angle ORP = 90^{\circ} + 90^{\circ} = 180^{\circ}$.
$5$. Since the sum of a pair of opposite angles in the quadrilateral $QORP$ is $180^{\circ}$,it is a cyclic quadrilateral.
Hence proved.