MathDB
The line t through the centroid of triangle ABC

Source: Baltic Way 2006

December 4, 2010
geometrycircumcircletrapezoidgeometry proposed

Problem Statement

Let the medians of the triangle ABCABC intersect at point MM. A line tt through MM intersects the circumcircle of ABCABC at XX and YY so that AA and CC lie on the same side of tt. Prove that BXBY=AXAY+CXCYBX\cdot BY=AX\cdot AY+CX\cdot CY.