MathDB
nine-point circle generalized

Source: bulgaria 2011

May 30, 2011
geometrycircumcirclegeometry proposed

Problem Statement

Point OO is inside △ABC\triangle ABC. The feet of perpendicular from OO to BC,CA,ABBC,CA,AB are D,E,FD,E,F. Perpendiculars from AA and BB respectively to EFEF and FDFD meet at PP. Let HH be the foot of perpendicular from PP to ABAB. Prove that D,E,F,HD,E,F,H are concyclic.
Back to ProblemsView on AoPS