Augustin-Louis Cauchy

Definition and stakes

1911 Encyclopædia Britannica, Volume 5… (1911)

“ In mechanics, he made many researches, substituting the notion of the continuity of geometrical displacements for the principle of the continuity of matter. In optics, he developed the wave theory, and his name is associated with the simple dispersion formula. In elasticity, he originated the theory of stress, and his results are nearly as valuable as those of S. D. Poisson. His collected works, Œuvres complètes d’Augustin Cauchy, have been published in 27 volumes. ”
Source: Wikisource

Portrait of Florian Cajori Florian Cajori,  A History of Mathematics (1893)

“ A great revolution in the ideas of a function was brought about by Cauchy when, in a function as defined by Dirichlet, he gave the variables imaginary values, and when he extended the notion of a definite integral by letting the variable pass from one limit to the other by a succession of imaginary values along arbitrary paths. Cauchy established several fundamental theorems, and gave the first great impulse to the study of the general theory of functions. His researches were continued in France by Puiseux and Liouville. But more profound investigations were made in Germany by Riemann. ”
Source: Wikisource

Portrait of Louis Bertrand Louis Bertrand,  Saint Augustin

“ There, stretched on the grass under the shade of one of these spreading trees, they chatted gaily while listening to the broken song of the brook, as it flowed under the windows of the baths. They lived very close to nature, almost the life of field-tillers. The whole charm of Cassicium consisted in its silence, its peace, and, above all, its fresh air. Augustin's tired lungs breathed there a purer air than in Milan, where the humid summer heat is crushing. ”
Source: Gutenberg

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