John Wallis (1616–1703)
Born 1616 CE, died 1703 CE.
John Wallis (; 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.
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