Thomas Fantet de Lagny

Thomas Fantet de Lagny (1660 to 1734) was a French mathematician well known for his contributions to computational mathematics and for calculating pi to 112 correct decimal places. In 1719 he computed pi to 127 decimal places using Gregory's series for the arctangent, although only 112 of those decimals were correct, a record that stood until Jurij Vega reached 126 correct digits in 1789. He studied at a Jesuit college in Lyon and in the Faculty of Law at Toulouse, tutored the Noailles family in Paris, taught hydrography at Rochefort and later served as a librarian at the Bibliothèque du roi and briefly as deputy director of the Banque Générale. He became an associate of the Académie Royale des Sciences in 1695 and a pensionnaire in 1723. His published works include methods for extracting square and cubic roots and for approximating roots, printed in Paris in 1691 and 1692.