3 concurrent diagonals
Source: Austrian MO 2005 round 1
June 27, 2005
geometryparallelogramgeometric transformationhomothetyreflectiongeometry solved
Problem Statement
We're given two congruent, equilateral triangles and with parallel sides, but one has one vertex pointing up and the other one has the vertex pointing down. One is placed above the other so that the area of intersection is a hexagon (labelled counterclockwise). Prove that , and are concurrent.