MathDB
Collinearity of points on angle bisectors

Source: Moldova TST Problem 2

March 31, 2015
geometryincenterangle bisector

Problem Statement

Consider a triangle ABC\triangle ABC, let the incircle centered at II touch the sides BC,CA,ABBC,CA,AB at points D,E,FD,E,F respectively. Let the angle bisector of BIC\angle BIC meet BCBC at MM, and the angle bisector of EDF\angle EDF meet EFEF at NN. Prove that A,M,NA,M,N are collinear.