semicircle problem
Source: China south east mathematical Olympiad 2007 problem 2
July 12, 2013
geometrygeometric transformationreflectionparallelogramgeometry unsolved
Problem Statement
is the diameter of semicircle . , are two arbitrary points on semicircle . Point lies on line such that line is tangent to semicircle at . Line intersects line , at point , respectively. Prove that =.