Problem

Source: 2022 IMOC G5 https://artofproblemsolving.com/community/c6h2918249p26069468

Tags: geometry, midpoint, Concyclic



$P$ is a point inside $ABC$. $BP$, $CP$ intersect $AC, AB$ at $E, F$, respectively. $AP$ intersect $\odot (ABC)$ again at X. $\odot (ABC)$ and $\odot (AEF)$ intersect again at $S$. $T$ is a point on $BC$ such that $P T \parallel EF$. Prove that $\odot (ST X)$ passes through the midpoint of $BC$. proposed by chengbilly