Is it possible to divide the plane into polygons so that each polygon is transformed into itself under some rotation by 360/7 degrees about some point? All sides of these polygons must be greater than 1 cm.
(A polygon is the part of a plane bounded by one non-self-intersect-ing closed broken line, not necessarily convex.)(A. Andjans, Riga) rotationcombinatoricscombinatorial geometrygeometrygeometric transformation