French mathematician François Viète (or Franciscus Vieta, 1540-1603) is often called the “founder of modern algebra.” He introduced the use of letters as algebraic symbols (although Descartes [see ahead] introduced the convention of letters at the end of the alphabet [x, y, …] for unknowns and beginning of the alphabet [a, b, …] for knowns), and connected algebra with geometry and trigonometry. He also included trigonometric tables in his *Canon Mathematicus* (1571)—along with the theory behind their construction. This book was originally meant to be a mathematical introduction to his unpublished astronomical treatise, *Ad harmonicon coeleste.* (For more about Viète, see “Algebra” and “Geometry and Trigonometry.”)

Scottish mathematician John Napier first conceived the idea of logarithms.