Points K and L are chosen on the sides AB and BC of the isosceles △ABC (AB=BC) so that AK+LC=KL. A line parallel to BC is drawn through midpoint M of the segment KL, intersecting side AC at point N. Find the value of ∠KNL.
Problem
Source: Tournament of Towns Spring 2003 - Junior O-Level - Problem 3
Tags: geometry, trapezoid, geometry proposed