MathDB
Italian mathematical olympiad 2002, problem 3

Source:

February 13, 2012
geometrycircumcircletrigonometryperpendicular bisectorgeometry proposed

Problem Statement

Let AA and BB are two points on a plane, and let MM be the midpoint of ABAB. Let rr be a line and let RR and SS be the projections of AA and BB onto rr. Assuming that AA, MM, and RR are not collinear, prove that the circumcircle of triangle AMRAMR has the same radius as the circumcircle of BSMBSM.