Fermat, Pierre de

(1601-1665)

   mathematician

   Born in Beaumont-de-Lomagne, Pierre de Fermat was a magistrate who had a passion for mathematics. In his youth, with his friend blaise pascal,he made a series of investigations into the properties of figurative numbers. while studying the work of the ancient Greek mathematician Diophantus, Fermat became interested in a chapter on Pythagorean numbers—sets of three numbers for which the equation a2 + b2 = c2 is true. He wrote in the margin of the text, "I have discovered a truly remarkable proof which this margin is too small to contain." The result became known as Fermat's Last Theorem. From all his studies, Fermat derived an important method of calculating probabilities. He anticipated differential calculus with his method of finding the greatest and least ordinates of curved lines. He is also a precursor of analytical geometry (independently of rené descartes), and he is the discoverer of Fermat's Principle on the path of light, which is the basis of optical geometry.