Lagrange, Joseph Louis de, Comte 1736-1813
French mathematician

Born in Turin, Italy, he succeeded Leonhard Euler (1766) as director of the mathematical section of the Berlin Academy, having gained a European reputation by his work on the calculus of variations, celestial mechanics and the nature of sound. While in Prussia he read before the Berlin Academy some 60 dissertations on celestial mechanics, number theory, algebraic and differential equations. He returned to Paris in 1787 at the invitation of Louis XVI. Under Napoleon I he became a senator and a count and taught at the �cole Normale and the �cole Polytechnique. In 1788 he published Trait� de m�canique analytique, one of his most important works, in which mechanics is based entirely on variational principles, giving it a high degree of elegance. His work on the theory of algebraic equations was one of the major steps in the early development of group theory, considering permutations of the roots of an equation.