important math developments By aprimbas Jun 18, 1202 Leonardo Fibonnacci develops the Fibonnacci sequence Jun 18, 1540 Ferrari solves a quartic equation Jun 18, 1647 Descartes uses the term imaginary number Jun 18, 1665 Isaac Newton develops the fundamental theorem of calculus http://en.wikipedia.org/wiki/Fundamental_theorem_of_calculus Jun 18, 1691 Leibniz discovers technique of separation of variables http://en.wikipedia.org/wiki/Gottfried_Wilhelm_Leibniz