MathDB
Perpendicularity

Source: Indian RMO 1995 Problem 1

October 26, 2005
exterior angle

Problem Statement

In triangle ABCABC, KK and LL are points on the side BCBC (KK being closer to BB than LL) such that BCKL=BKCLBC \cdot KL = BK \cdot CL and ALAL bisects KAC\angle KAC. Show that ALAB.AL \perp AB.