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three circles of equal radius

Source: All-Russian Olympiad 1996, Grade 9, First Day, Problem 2

April 18, 2013
geometry proposedgeometry

Problem Statement

The centers O1O_1; O2O_2; O3O_3 of three nonintersecting circles of equal radius are positioned at the vertices of a triangle. From each of the points O1O_1; O2O_2; O3O_3 one draws tangents to the other two given circles. It is known that the intersection of these tangents form a convex hexagon. The sides of the hexagon are alternately colored red and blue. Prove that the sum of the lengths of the red sides equals the sum of the lengths of the blue sides.
D. Tereshin