François Viète

François Viète (1540 to 1603), known in Latin as Franciscus Vieta, was a French mathematician whose work on a new algebra was an important step towards modern algebra, because he used letters as parameters in equations. For this he is sometimes called the father of modern algebraic notation. He was a lawyer by trade and served as a privy councillor to both Henry III and Henry IV of France. Born at Fontenay-le-Comte, he studied law at Poitiers, graduating in 1559, and later entered the service of the Huguenot Parthenay family, where he tutored the young Catherine de Parthenay and wrote for her treatises on astronomy and trigonometry. In these he used decimal numbers some twenty years before Stevin and noted the elliptic orbit of the planets decades before Kepler.