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Find angle

Source: Sharygin Geometry Olympiad 2012 - Problem 6

April 28, 2012
symmetrygeometrycircumcircleinradiusincentertrigonometrytrapezoid

Problem Statement

Point C1C_{1} of hypothenuse ACAC of a right-angled triangle ABCABC is such that BC=CC1BC = CC_{1}. Point C2C_{2} on cathetus ABAB is such that AC2=AC1AC_{2} = AC_{1}; point A2A_{2} is defined similarly. Find angle AMCAMC, where MM is the midpoint of A2C2A_{2}C_{2}.