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Famous Theorem of R...

Source: INAMO 2020 P6

October 14, 2020
geometryCyclic Quadrilateralsparallel

Problem Statement

Given a cyclic quadrilateral ABCDABCD. Let XX be a point on segment BCBC (X≠BCX \not= BC) such that line AXAX is perpendicular to the angle bisector of ∠CBD\angle CBD, and YY be a point on segment ADAD (Y≠D)Y \not= D) such that BYBY is perpendicular to the angle bisector of ∠CAD\angle CAD. Prove that XYXY is parallel to CDCD.
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