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In the plane there exists finite interconnections

Source: IMO Longlist 1989, Problem 63

September 18, 2008
geometrygeometric transformationreflectiongeometry unsolved

Problem Statement

Let li, l_i, i \equal{} 1,2,3 be three non-collinear straight lines in the plane, which build a triangle, and fi f_i the axial reflections in li l_i. Prove that for each point P P in the plane there exists finite interconnections (compositions) of the reflections of fi f_i which carries P P into the triangle built by the straight lines li, l_i, i.e. maps that point to a point interior to the triangle.