John Wallis

John Wallis
Born3 December [O.S. 23 November] 1616
Ashford, Kent, England
Died8 November 1703(1703-11-08) (aged 86) [O.S. 28 October 1703]
EducationFelsted School, Emmanuel College, Cambridge
Known forWallis product
Inventing the symbol
Extending Cavalieri's quadrature formula
Coining the term "momentum"
SpouseSusanna Glynde (m. 1645)
Children3, including Anne, Lady Blencowe
Scientific career
FieldsMathematics
Institutions
Academic advisorsWilliam Oughtred
Notable studentsWilliam Brouncker

John Wallis (/ˈwɒlɪs/; Latin: Wallisius; 3 December [O.S. 23 November] 1616 – 8 November [O.S. 28 October] 1703) was an English clergyman and mathematician, who is given partial credit for the development of infinitesimal calculus.

Between 1643 and 1689 Wallis served as chief cryptographer for Parliament and, later, the royal court. He extended Cavalieri's method of indivisibles through the use of interpolation. Applying Kepler's principle of continuity, he developed techniques for the evaluation of integrals. He is credited with introducing the symbol ∞ to represent the concept of infinity. He similarly used 1/∞ for an infinitesimal. He was a contemporary of Isaac Newton and one of the greatest intellectuals of the early modern mathematics.