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MathNet 2026 — Part 07 Question 34

Math Olympiad Vault · MathNet 2026 — Part 07

Question 34

Let $ABC$ be an acute triangle such that $AB$ is the shortest side of the triangle. Let $D$ be the midpoint of the side $AB$ and $P$ be an interior point of the triangle such that
$$
\measuredangle CAP=\measuredangle CBP=\measuredangle ACB
$$
Denote by $M$ and $N$ the feet of the perpendiculars from $P$ to $BC$ and $AC$, respectively. Let $p$ be the line through $M$ parallel to $AC$ and $q$ be the line through $N$ parallel to $BC$. If $p$ and $q$ intersect at $K$ prove that $D$ is the circumcenter of triangle $MNK$.