MathDB

2

Part of 2008 IberoAmerican

Problems(1)

lines concurrent with external bisector

Source: Iberoamerican Olympiad 2008, problem 2

9/24/2008
Given a triangle ABC ABC, let r r be the external bisector of ∠ABC \angle ABC. P P and Q Q are the feet of the perpendiculars from A A and C C to r r. If CP \cap BA \equal{} M and AQ \cap BC\equal{}N, show that MN MN, r r and AC AC concur.
trigonometryprojective geometrygeometrytrig identitiesLaw of Sinesangle bisectorgeometry proposed