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Inequality with triangles and squares

Source: Brazilian Mathematical Olympiad 2018 - Q1

November 16, 2018
Inequalitygeometrytriangle inequalityinequalitiesBrazilian Math OlympiadBrazilian Math Olympiad 2018

Problem Statement

We say that a polygon PP is inscribed in another polygon QQ when all vertices of PP belong to perimeter of QQ. We also say in this case that QQ is circumscribed to PP. Given a triangle TT, let ll be the maximum value of the side of a square inscribed in TT and LL be the minimum value of the side of a square circumscribed to TT. Prove that for every triangle TT the inequality L/l2L/l \ge 2 holds and find all the triangles TT for which the equality occurs.