A Saccheri Quadrilateral A Saccheri quadrilateral, or KhayyamSaccheri quadrilateral,[1] is a foursided figure. It has a base, AB, two equal legs standing at right angles to it, AC and BD, and nonobtuse angles at the summit, CD. It is composed entirely of straight lines. It was discovered by Omar Khayyam and is named after Giovanni Gerolamo Saccheri.[1] A rectangle is a special case of a Saccheri quadrilateral in which all four angles are right angles. A Saccheri quadrilateral is composed of two equal Lambert quadrilaterals. Notes 1. ^ a b Boris Abramovich Rozenfelʹd (1988), A History of NonEuclidean Geometry: Evolution of the Concept of a Geometric Space, p. 65. Springer, ISBN 0387964584. References * George E. Martin, The Foundations of Geometry and the NonEuclidean Plane, SpringerVerlag, 1975 Retrieved from "http://en.wikipedia.org/"

