MathDB
Midpoint of XY is foot of altitude from C

Source: Baltic Way 2010

November 19, 2010
geometryperpendicular bisectorgeometry proposed

Problem Statement

Assume that all angles of a triangle ABCABC are acute. Let DD and EE be points on the sides ACAC and BCBC of the triangle such that A,B,D,A, B, D, and EE lie on the same circle. Further suppose the circle through D,E,D,E, and CC intersects the side ABAB in two points XX and YY. Show that the midpoint of XYXY is the foot of the altitude from CC to ABAB.