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International Mathematical Olympiad 2014 — Official contest Question 4

IMO · International Mathematical Olympiad 2014 — Official contest

Question 4

Let $P$ and $Q$ be on segment $BC$ of an acute triangle $ABC$ such that $\angle PAB=\angle BCA$ and $\angle CAQ=\angle ABC$. Let $M$ and $N$ be points on $\overline{AP}$ and $\overline{AQ}$, respectively, such that $P$ is the midpoint of $\overline{AM}$ and $Q$ is the midpoint of $\overline{AN}$. Prove that $\overline{BM}$ and $\overline{CN}$ meet on the circumcircle of $\triangle ABC$.