Question 93
Suppose $O$ is the circumcenter of an acute triangle $\triangle ABC$, $P$ is a point inside $\triangle AOB$, and $D$, $E$, $F$ are the projections of $P$ on three sides $BC$, $CA$, $AB$ of $\triangle ABC$ respectively. Prove that a parallelogram with $FE$ and $FD$ as adjacent sides lies inside $\triangle ABC$. (posed by Leng Gangsong)
