Question 21
Let $A$ be a point outside a circle $\Gamma$. We lead two tangents $[A T]$ and $[A T']$ from $A$. Let $M$ and $M'$ be the media of $[A T]$ and $[A T']$. Let $P$ be a point of $[M M']$. Note $[U V]$ The string of $\Gamma$ such as $(P U)$ and $(P V)$ are tangent to $\Gamma$. The right $(U V)$ cuts $[M M']$ in $Q$. Show that the triangle $P A Q$ is rectangle.