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Prove that $AH$ and $CK$ are parallel.

Source: Moldova EGMO TST 2021

February 4, 2023
geometry

Problem Statement

Let ABCDABCD be a square and EE a on point diagonal (AC)(AC), different from its midpoint. HH and KK are the orthoceneters of triangles ABEABE and ADEADE. Prove that AHAH and CKCK are parallel.