Problem

Source: Mongolian Mathematical Olympiad P2

Tags: geometry



In an acute triangle $ABC$ the points $D, E$ are the feet of the altitudes through $B, C$ respectively. Let $L$ be the point on segment $BD$ such that $AD=DL$. Similarly, let $K$ be the point on segment $CE$ such that $AE=EK$. Let $M$ be the midpoint of $KL$. The circumcircle of $ABC$ intersect the lines $AL$ and $AK$ for a second time at $T, S$ respectively. Prove that the lines $BS, CT, AM$ are concurrent.