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MathNet 2014 Question 92

Math Olympiad Vault · MathNet 2014

Question 92

Let $ABC$ be an acute triangle such that $|AC| \gt |BC|$. Let $H$ be the orthocentre of that triangle, $N$ the foot of the altitude from $B$, and $P$ the midpoint of the side $AB$. The circumcircles of the triangles $ABC$ and $CHN$ intersect in $C$ and $D$. Prove that the points $B, D, N$ and $P$ lie on the same circle.