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Geometric inequality

Source: Lusophon Math Olympiad 2020 Day 1 #3

November 1, 2020
inequalitiesgeometrygeometric inequality

Problem Statement

Let ABCABC be a triangle and on the sides we draw, externally, the squares BADE,CBFGBADE, CBFG and ACHIACHI. Determine the greatest positive real constant kk such that, for any triangle ABC\triangle ABC, the following inequality is true: [DEFGHI]k[ABC][DEFGHI]\geq k\cdot [ABC] Note: [X][X] denotes the area of polygon XX.