MathDB

1

Part of 2015 Singapore MO Open

Problems(1)

SMO 2015 open q1

Source: SMO 2015 open

3/31/2018
In an acute-angled triangle △ABC\triangle ABC, 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.
geometry