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Lengths of sides of ABC form an arithmetic progression

Source: Romanian MO 2010 Grade 9

August 6, 2012
geometry unsolvedgeometry

Problem Statement

Prove that there is a similarity between a triangle ABCABC and the triangle having as sides the medians of the triangle ABCABC if and only if the squares of the lengths of the sides of triangle ABCABC form an arithmetic sequence.
Marian Teler & Marin Ionescu