Problem

Source: Indian RMO 2013 Mumbai Region Problem 1

Tags: geometry, circumcircle, trapezoid, geometry unsolved



Let $ABC$ be an isosceles triangle with $AB=AC$ and let $\Gamma$ denote its circumcircle. A point $D$ is on arc $AB$ of $\Gamma$ not containing $C$. A point $E$ is on arc $AC$ of $\Gamma$ not containing $B$. If $AD=CE$ prove that $BE$ is parallel to $AD$.