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BALTIC-WAY 2024 Problem 13

    Let ABCA B C be an acute triangle with orthocentre HH. Let DD be a point outside the circumcircle of triangle ABCA B C such that ∠ABD=∠DCA\angle A B D=\angle D C A. The reflection of ABA B in BDB D intersects CDC D at XX. The reflection of ACA C in CDC D intersects BDB D at YY. The lines through XX and YY perpendicular to ACA C and ABA B, respectively, intersect at PP. Prove that points D,PD, P and HH are collinear.

    Dataset text NuminaMath olympiads. Quoted with source.

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