The name non-Euclidean was used by Gauss to describe a system of geometry which differs from Euclid's in its properties of parallelism. Such a system was developed independently by Bolyai in Hungary and Lobatschewsky in Russia, about 120 years ago. Another system, differing more radically from Euclid's, was suggested later by Riemann in Germany and Cayley in England. The subject was unified in 1871 by Klein, who gave the names of parabolic, hyperbolic, and elliptic to the respective system...

For over eighty years this delightful classic has provided entertainment through mathematical problems commonly known as recreations. Although they often involve fundamental mathematical methods and notions, their chief appeal is as games or puzzles rather than the usefulness of their conclusions.This new edition upholds the original, but the terminology and treatment of problems have been updated and much new material has been added. There are new selections on polyominoes and the...