PFAFF, JOHANN FRIEDRICH

born Dec. 22, 1765, Stuttgart, Wrttemberg died April 21, 1825, Halle, Saxony German mathematician who proposed the first general method of integrating partial differential equations of the first order. Pfaff was professor of mathematics at the University of Helmstedt from 1788 until 1810, when he was appointed professor of mathematics at the University of Halle. He made notable contributions to calculus, the theory of series, and the solution of differential equations. He completed his work on the general method of partial differential equation integration in 1814-15. The term Pfaffian problem was originated in his honour. Among his published works are Disquisitiones analyticae (1797; "Analytic Works") and Observationes ad Euleri institutiones calculi integralis ("Observations of Eulerian Methods of the Integral Calculus").