If two circles touch each other externally then the point of contact will lie on the line segment joining the two centres -Prove it.

Prove that the tangent and the radius through the point of contact of a circle are perpendicular to each other.

The radius of a circle with centre $O$ is $5 cm$. $P$ is a point at a distance $13 cm$ from $O$. $PQ$ and $PR$ are two tangents to this circle. Find the area of the quadrilateral $PQOR$.