A cyclic quad
Source: Indian RMO 2002 Problem 5
October 27, 2005
Problem Statement
The circumference of a circle is divided into eight arcs by a convex quadrilateral with four arcs lying inside the quadrilateral and the remaining four lying outside it. The lengths of the arcs lying inside the quadrilateral are denoted by in counter-clockwise direction. Suppose . Prove that is cyclic.