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Dividing rectangle in to dominoes and drawing diagonals...

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February 13, 2011
geometryrectangleanalytic geometrygeometric transformationreflectioncombinatorics unsolvedcombinatorics

Problem Statement

A rectangle is divided into 2×12\times 1 and 1×21\times 2 dominoes. In each domino, a diagonal is drawn, and no two diagonals have common endpoints. Prove that exactly two corners of the rectangle are endpoints of these diagonals.