MathDB
Quadrilateral

Source: Cono Sur 2002

August 14, 2017
geometrycono sur

Problem Statement

Let ABCDABCD be a convex quadrilateral such that your diagonals ACAC and BDBD are perpendiculars. Let PP be the intersection of ACAC and BDBD, let MM a midpoint of ABAB. Prove that the quadrilateral ABCDABCD is cyclic, if and only if, the lines PMPM and DCDC are perpendiculars.
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