IGO 2017 I5

Let $X,Y$ be two points on the side $BC$ of triangle $ABC$ such that $2XY=BC$ ( $X$ is between $B,Y$ ). Let $AA'$ be the diameter of the circumcirle of triangle $AXY$ . Let $P$ be the point where $AX$ meets the perpendicular from $B$ to $BC$ , and $Q$ be the point where $AY$ meets the perpendicular from $C$ to $BC$ . Prove that the tangent line from $A'$ to the circumcircle of $AXY$ passes through the circumcenter of triangle $APQ$ .

Proposed by Iman Maghsoudi