Karl Weierstrass

Karl Theodor Wilhelm Weierstrass was born on 31 October 1815 in Germany. He studied mathematics but left university without a degree, trained as a school teacher, and spent years teaching mathematics, physics, botany, and gymnastics. Later he received an honorary doctorate and became professor of mathematics in Berlin. He formalized the definition of the continuity of a function and complex analysis, proved the intermediate value theorem and the Bolzano-Weierstrass theorem, and used the latter to study the properties of continuous functions on closed bounded intervals. He died on 19 February 1897, often cited as the "father of modern analysis".