There are 2 NRICH Mathematical resources connected to Non Euclidean Geometry, you may find related items under 3D Geometry, Shape and Space.Broad Topics > 3D Geometry, Shape and Space > Non Euclidean Geometry
This article outlines the underlying axioms of spherical geometry giving a simple proof that the sum of the angles of a triangle on the surface of a unit sphere is equal to pi plus the area of the. . . .
This article (the first of two) contains ideas for investigations. Space-time, the curvature of space and topology are introduced with some fascinating problems to explore.