Abstract
HENRI-LéON LEBESGUE was born in 1875 at Beauvais, and after studying at the ficole Normale Superieure, taught from 1899 until 1902 in the Lycee at Nancy, where he wrote his famous these de Doctorat “Integrate longueur, aire”, which was published in the Annali di Matematica, in 1902. After holding academic posts at Rennes and Poitiers, he was appointed in 1910 lecturer at the Faculty of Sciences of Paris, in 1921 professor of mathematics at the College de France, and in 1922 a member of the Academy of Sciences. Prof. Lebesgue's reputation was first made by his definitions of the functional operations of integration and derivation, which are of such generality that they may be applied to classes of functions vastly more extensive than the restricted classes to which earlier definitions had been applicable. It was Cauchy who first replaced the geometrical idea of an integral, as an area, by a precise arithmetical definition, regarding it as the limit of a sum of elements f(x)ΔxwhenΔxtends to zero; and on this basis he proved theorems of existence and uniqueness. Riemanh generalised Cauchy's conception by extending it to certain functions which were discontinuous at points forming sets dense everywhere; but the functions integrable in Riemann's sense are still a limited class.
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Prof Henri-Léon Lebesgue, For, Mem R.S. Nature 133, 714 (1934). https://doi.org/10.1038/133714b0
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DOI: https://doi.org/10.1038/133714b0