Problem

Source: 2023 IGMO Round 2 p5 International Gamma Mathematics Olympiad

Tags: geometry, concurrency, concurrent



Let $\vartriangle ABC$ be an acute-angled scalene (i.e. non-isosceles) triangle. $D$ and $E$ are the foot of $B$-altitude and C-altitude of $\vartriangle ABC$ respectively. $M$ is the midpoint of $BC$. The circumcircles of $\vartriangle BEM$ and $\vartriangle CDM$ meet at $F$ (other than $M$). $X$ and $Y$ are the points of projection of $F$ on $BD$ and $CE$ respectively. Prove that $AF$ and $XY$ meet at the circumcircle of $\vartriangle DEM$.