Varignon's theorem

For the theorem about the moment of a force, see Varignon's theorem (mechanics).
Area(EFGH) = (1/2)Area(ABCD)

In Euclidean geometry, Varignon's theorem holds that the midpoints of the sides of an arbitrary quadrilateral form a parallelogram, called the Varignon parallelogram. It is named after Pierre Varignon, whose proof was published posthumously in 1731.[1]

  1. ^ Peter N. Oliver: Pierre Varignon and the Parallelogram Theorem[permanent dead link]. Mathematics Teacher, Band 94, Nr. 4, April 2001, pp. 316-319