MathDB
2019 Central American and Caribbean Mathematical Olympiad, P3

Source:

June 18, 2019
geometrycircumcircle

Problem Statement

Let ABCABC be a triangle and Γ\Gamma its circumcircle. Let DD be the foot of the altitude from AA to the side BCBC, MM and NN the midpoints of ABAB and ACAC, and QQ the point on Γ\Gamma diametrically opposite to AA. Let EE be the midpoint of DQDQ. Show that the lines perpendicular to EMEM and ENEN passing through MM and NN, respectively, meet on ADAD.