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angle chasing starting with an isosceles right triangle.

Source: 2012 Sharygin Geometry Olympiad Final Round 9.5

August 3, 2018
Angle Chasingisoscelesright trianglegeometry

Problem Statement

Let ABCABC be an isosceles right-angled triangle. Point DD is chosen on the prolongation of the hypothenuse ABAB beyond point AA so that AB=2ADAB = 2AD. Points MM and NN on side ACAC satisfy the relation AM=NCAM = NC. Point KK is chosen on the prolongation of CBCB beyond point BB so that CN=BKCN = BK. Determine the angle between lines NKNK and DMDM.
(M.Kungozhin)
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