MathDB
Intersection of Three Lines

Source: Spring 2006 Tournament of Towns Junior A-Level #3

April 15, 2015
geometry

Problem Statement

On sides ABAB and BCBC of an acute triangle ABCABC two congruent rectangles ABMNABMN and LBCKLBCK are constructed (outside of the triangle), so that AB=LBAB = LB. Prove that straight lines AL,CMAL, CM and NKNK intersect at the same point.
(5 points)