MathDB
Soviet Union 7

Source: IMO LongList 1959-1966 Problem 50

September 2, 2004
geometryinequalitiestrigonometrygeometry proposed

Problem Statement

For any quadrilateral with the side lengths a,a, b,b, c,c, dd and the area S,S, prove the inequalitySa+c2b+d2.S\leq \frac{a+c}{2}\cdot \frac{b+d}{2}.