Karl Wilhelm Feuerbach (30 May 1800 – 12 March 1834) was a German geometer and the son of legal scholar Paul Johann Anselm Ritter von Feuerbach, and the brother of philosopher Ludwig Feuerbach. After receiving his doctorate at age 22, he became a professor of mathematics at the Gymnasium at Erlangen. In 1822 he wrote a small book on mathematics noted mainly for a theorem on the nine-point circle, which is now known as Feuerbach's theorem. In 1827 he introduced homogeneous coordinates, independently of Möbius.
Works
Eigenschaften einiger merkwürdigen Punkte des geradlinigen Dreiecks und mehrerer durch sie bestimmten Linien und Figuren. Eine analytisch-trigonometrische Abhandlung (Monograph ed.), Nürnberg: Wiessner, 1822. online book at Google Books ("Properties of some special points in the plane of a triangle, and various lines and figures determined by these points: an analytic-trigonometric treatment")
Grundriss zu analytischen Untersuchungen der dreyeckigen Pyramide ("Foundations of the analytic theory of the triangular pyramid")