MathDB
Quad ineq

Source: Indian RMO 1997 Problem 4

October 26, 2005
geometryindiaRMOinequalities

Problem Statement

In a quadrilateral ABCDABCD, it is given that ABAB is parallel to CDCD and the diagonals ACAC and BDBD are perpendicular to each other. Show that (a) ADBCABCDAD \cdot BC \geq AB \cdot CD (b) AD+BCAB+CD.AD + BC \geq AB + CD.