MathDB
Delta 2.9

Source:

June 28, 2020
Delta 2

Problem Statement

Let ABCABC be a triangle and let DD and EE be points on sides ABAB and ACAC, respectively, such that DEBCDE \parallel BC. Let PP be any point interior to triangle ADEADE, and let FF and GG be the intersections of DEDE with the lines BPBP and CPCP, respectively. Let QQ be the second intersection point of the circumcircles of triangles PDGPDG and PFEPFE. Prove that the points A,P,A,P, and QQ are collinear.