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the squares that have $BC$ and $AD$ as diagonals also have a common vertex

Source: Moldova TST 2000

August 7, 2023
geometry

Problem Statement

Let ABCDABCD be a convex quadrilateral. Two squares are constructed such that ABAB{} and CDCD{} are their diagonals. Show that if these squares have a common vertex inside ABCDABCD, then the squares that have BCBC{} and ADAD{} as diagonals also have a common vertex inside ABCDABCD.