Fermat, Pierre de (pyĕr də fĕrmäˈ) [key], 1601–65, French mathematician. A magistrate whose avocation was mathematics, Fermat is known as a founder of modern number theory and probability theory. He also did much to establish coordinate geometry (see Cartesian coordinates) and invented a number of methods for determining maxima and minima that were later of use to Newton in applying the calculus. He noted without proof, although he claimed to have discovered one, the assertion now known as **Fermat's Last Theorem,** which states that the equation *x* ^{ n } + *y* n =

See M. S. Mahoney, *The Mathematical Career of Pierre de Fermat 1601–1665* (2d rev. ed. 1994); A. D. Aczel, *Fermat's Last Theorem* (1996); S. Singh and J. Lynch, *Fermat's Enigma* (1998).

*The Columbia Electronic Encyclopedia,* 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.