45. Exemplar exercise problems XIX

From an external point $P$, two tangents, $PA$ and $PB$ are drawn to a circle with centre $O$. At one point $E$ on the circle tangent is drawn which intersects $PA$ and $PB$ at $C$ and $D$, respectively. If $PA = 10 \ cm$, find the perimeter of the triangle $PCD$.

 

Perimeter $=$ $cm$