SMO 2015 open q1
Source: SMO 2015 open
March 31, 2018
geometry
Problem Statement
In an acute-angled triangle , D is the point on BC such that AD bisects ∠BAC,
E and F are the feet of the perpendiculars from D onto AB and AC respectively. The
segments BF and CE intersect at K. Prove that AK is perpendicular to BC.