MathDB
Prove concurrence involving excirlce

Source: Romanian NO, grade ix, p.3

October 3, 2019
geometry

Problem Statement

Let ABC ABC be a triangle, Ia I_a be center of the A-excircle. A\text{-excircle}. This excircle intersects the lines AB,AC, AB, AC, at P, P, respectively, Q. Q. The line PQ PQ intersects the lines IaB,IaC I_aB,I_aC at D, D, respectively, E. E. Let A1 A_1 be the intersection of DC DC with BE, BE, and define, analogously, B1,C1. B_1,C_1. Show that AA1,BB1,CC1 AA_1,BB_1,CC_1 are concurrent.
Back to ProblemsView on AoPS