Augustin-Louis Cauchy

Augustin-Louis Cauchy was a French mathematician who was among the first to place calculus on a rigorous logical foundation, defining concepts such as the limit, continuity and convergence with a precision earlier mathematicians had largely lacked. Teaching at the Ecole Polytechnique in Paris in the 1820s, Cauchy's textbooks on analysis established much of the careful, proof-based approach to calculus that became standard in mathematics education afterward. He made extensive contributions to complex analysis, including the Cauchy integral theorem describing how integrals of complex functions behave, and to the theory of permutation groups that later fed into the development of abstract algebra. An extraordinarily prolific mathematician, Cauchy published roughly 800 papers across his career, covering topics from mathematical physics to elasticity theory to number theory, and his name is attached to a wide range of theorems, sequences and inequalities still taught throughout modern mathematics.