MathDB
Circumcircle of half of an isosceles triangle

Source: Junior Turkish Mathematical Olympiad 2011 P2

July 2, 2012
geometrycircumcircleanalytic geometrygraphing linesslopepower of a pointradical axis

Problem Statement

Let ABCABC be a triangle with AB=AC|AB|=|AC|. DD is the midpoint of [BC][BC]. EE is the foot of the altitude from DD to ACAC. BEBE cuts the circumcircle of triangle ABDABD at BB and FF. DEDE and AFAF meet at GG. Prove that DG=GE|DG|=|GE|