MathDB
Points A, E, S and C lie on the same circle [Slovenia 2010]

Source:

November 16, 2010
geometrycircumcirclegeometry proposed

Problem Statement

Let ABCABC be an acute triangle with AB>AC.|AB| > |AC|. Let DD be a point on the side ABAB, such that the angles ACD\angle ACD and CBD\angle CBD are equal. Let EE denote the midpoint of BD,BD, and let SS be the circumcenter of the triangle BCD.BCD. Prove that the points A,E,SA, E, S and CC lie on the same circle.