**Augustin Louis Cauchy** He was born on August 21, 1789, and died May 23, 1857.

It was a French mathematician and physicist who proved (1811) that the angles of a convex polyhedron are determined by their faces (the flat surfaces that form a geometric solid).

Numerous terms in mathematics have his name, for example, Cauchy's integral theorem in complex function theory and Cauchy-Kovalevskaya, the existing theorem for solving partial differential equations. Cauchy was the first to carefully study the conditions for infinite SERIES CONVERGENCE; He also gave a rigorous definition of an integral independent of the process of differentiation and developed the mathematical theory of elasticity. His texts, Cours d'analyse (Course in Analysis, 1821) and the 4 volumes Exercises d'analyse et de physique mathematique (Exercises in Analysis and Mathematical Physics, 1840-47) were highly influential.

Bell, E.T., Men of Mathematics (1937); Muir, Jane, Of Men and Numbers (1961).