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 This book was originally meant to be a mathematical introduction to his unpublished astronomical treatise, Ad harmonicon coeleste.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.