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CK + KM = BL + LM if AK = AL = BC

Source: 2022 Saudi Arabia November Camp Test 2.2 BMO + EGMO TST

November 1, 2022
geometryequal segments

Problem Statement

Given is an acute triangle ABCABC with BC<CA<ABBC < CA < AB. Points KK and LL lie on segments ACAC and ABAB and satisfy AK=AL=BCAK = AL = BC. Perpendicular bisectors of segments CKCK and BLBL intersect line BCBC at points PP and QQ, respectively. Segments KPKP and LQLQ intersect at MM. Prove that CK+KM=BL+LMCK + KM = BL + LM.