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BP=PQ wanted, CD=CE, right isosceles (2021 Novosibirsk Oral Geo Oly 8.5)

Source:

May 24, 2021
geometryright triangleisoscelesequal segments

Problem Statement

On the legs ACAC and BCBC of an isosceles right-angled triangle with a right angle CC, points DD and EE are taken, respectively, so that CD=CECD = CE. Perpendiculars on line AEAE from points CC and DD intersect segment ABAB at points PP and QQ, respectively. Prove that BP=PQBP = PQ.