Non-Euclidean geometry considers Areas the place Euclid's parallel postulate fails. Saccheri initial examined this sort of geometries in 1733 but sought only to disprove them. Gauss, Bolyai and Lobachevsky independently learned them one hundred decades later. Amongst the probable quotient spaces that aren't automatically manifolds, orbifolds and CW complexes are http://valves-and-fittings51593.blogsidea.com/175980/about-manifold-valve