Problem

Source: Mediterranean Mathematical Olympiad 2022 P4 MMC

Tags: geometry, tangent



The triangle $ABC$ is inscribed in a circle $\gamma$ of center $O$, with $AB < AC$ . A point $D$ on the angle bisector of $\angle BAC$ and a point $E$ on segment $BC$ satisfy $OE$ is parallel to $AD$ and $DE \perp BC$. Point $K$ lies on the extension line of $EB$ such that $EA = EK$. A circle pass through points $A,K,D$ meets the extension line of $BC$ at point $P$, and meets the circle of center $O$ at point $Q\ne A$. Prove that the line $PQ$ is tangent to the circle $\gamma$.