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Polygon with a center of symmetry

Source: Problem 3, Polish NO 1988

October 16, 2005
symmetrygeometryparallelogramgeometry unsolved

Problem Statement

WW is a polygon which has a center of symmetry SS such that if PP belongs to WW, then so does PP', where SS is the midpoint of PPPP'. Show that there is a parallelogram VV containing WW such that the midpoint of each side of VV lies on the border of WW.