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AB=BQ wanted, AB\\ PC , PM_|_ BM, median (2021 Kyiv City MO 9.5)

Source:

February 15, 2021
geometryequal segmentsmedian

Problem Statement

Let BMBM be the median of the triangle ABCABC, in which AB>BCAB> BC. Point PP is chosen so that ABPCAB \parallel PC andPMBM PM \perp BM. The point QQ is chosen on the line BPBP so that AQC=90o\angle AQC = 90^o, and the points BB and QQ lie on opposite sides of the line ACAC. Prove that AB=BQAB = BQ.
(Mikhail Standenko)