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ASU 351 All Soviet Union MO 1983 expand disks by 2/\sqrt3 times

Source:

July 28, 2019
geometrycombinatorial geometrycircles

Problem Statement

Three disks touch pairwise from outside in the points X,Y,ZX,Y,Z. Then the radiuses of the disks were expanded by 2/32/\sqrt3 times, and the centres were reserved. Prove that the triangle XYZXYZ is completely covered by the expanded disks.