1660-1718

French mathematician who was tutored by an uncle before entering a Jesuit college in Lyon. While tutoring in mathematics for a private family over a period of 10 years, he collaborated with l'Hospital in Paris. After he had been active in the Académie des Sciences, he was offered a professorship at Rochefort, where he worked on trigonometry and made use of binary arithmetic. Streets in Paris have been named for him—passage de Lagny and rue de Lagny—and he was awarded the honor of a fellowship of the Royal Society in 1718.