WEIERSTRASS, KARL (1815-1897), German mathema tician, was born at Ostenfelde on Oct. 31, 1815. He studied juris prudence at Bonn, and later went to Munster to study under Gudermann, who was interested in the theory of functions. Weier strass wrote a paper on the development of modular func tions for his teacher's examination, and so started the work in mathematics with which his name is associated. He became a teacher of mathematics at the "gymnasium" at Deutsche-Crone (1842-48) and then at the Collegium Hoseanum in Braunsberg (1848-56). In 1856 he was appointed extraordinary professor of mathematics at Berlin and lecturer at the school of technology. He was appointed ordinary professor in 5864. He died in Berlin on Feb. 19, 1897.
Weierstrass' work in mathematics was mainly on the theory of functions; his was the most notable work on this subject since that of Abel and Jacobi. He published very little himself, but embodied his works in his lectures. These were taken down by the students and afterwards collected in Gesammelte Abhandlung en; vols. i., ii. and iii. and 1903) contained his lec
tures, vol. iv. (1902) on Abelian functions, vols. v. and vi. (1915) on elliptic functions, vol vii. on the calculus of variations, and vol. viii. on analytic functions. He worked on the functions of real variables, devised tests for the convergence of series, and dealt with converging infinite products. He also dealt with the theory of bilinear and quadratic forms. Weierstrass developed the theory of functions of complex variables to such an extent that he put this subject on a fresh basis. He also made notable con tributions to the theory of periodic functions, elliptic functions and the calculus of variations. Although his work was on pure mathematics, he was interested in its applications, and influenced a number of his students to work on applied mathematics.
He edited Steiner's Gesammelte Werke (2 vols., 1881-82), and was co-editor with Kummer of Crelle's Journal.