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CL= BC if AB=AD

Source: All-Russian MO 2009 Regional 11.6

August 27, 2024
geometryequal segments

Problem Statement

Point DD on side BCBC of acute triangle ABC is such that AB=ADAB=AD. The circumcircle of triangle ABDABD intersects side ACAC at points AA and KK. Line DKDK intersects the perpendicular drawn from BB on ACAC, at the point LL. Prove that CL=BCCL= BC
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