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Square in a circle

Source: Sharygin Geometry Olympiad 2012 - Problem 17

April 28, 2012
geometryanalytic geometrygeometry unsolved

Problem Statement

A square ABCDABCD is inscribed into a circle. Point MM lies on arc BCBC, AMAM meets BDBD in point PP, DMDM meets ACAC in point QQ. Prove that the area of quadrilateral APQDAPQD is equal to the half of the area of the square.