Thomas Fantet de Lagny

Thomas Fantet de Lagny was a French mathematician, born on 7 November 1660 and dead on 11 April 1734, known for his work in computational mathematics and for calculating pi to 112 correct decimal places. The son of a royal official in Grenoble, he became passionate about mathematics at the Jesuit college in Lyon, studied law at Toulouse and in 1686 went to Paris as a mathematics tutor to the Noailles family, collaborating with L'Hospital. He became an associate of the Académie Royale des Sciences in 1695, was professor of hydrography at Rochefort from 1697, and returned to Paris in 1714 as librarian at the Bibliothèque du roi. In 1719 he computed pi to 127 places using Gregory's series for the arctangent, of which 112 were correct, a record that stood until Jurij Vega's 126 digits in 1789. His books include methods for extracting roots of 1691 and 1692 and the Analyse générale of 1733.