Fourier, Joseph

(1768-1830)

   mathematician

   Born in Auxerre, Joseph Fourier, who was one of the leading instructors at the École polytechnique, as a scientist took part in Napoléon Bonaparte's (see napoléon i) expedition to Egypt (1798). His works, concerning the theory of heat, led him to the discovery of the series that bears his name and which allowed the expression of a periodic function as the sum of sines and cosines. Altogether, Fourier's theories constitute one of the most useful applications of mathematics to physics and have assured their author a leading place among the mathematicians of the 19th century. He also developed an important theorem on the roots of algebraic equations, perfecting that of rené descartes. Fourier was elected to the Academy of Sciences in 1817, and to the Académie Française in 1826.