Karl Wilhelm Feuerbach (30 May 1800 – 12 March 1834) was a German
geometer
A geometer is a mathematician whose area of study is geometry.
Some notable geometers and their main fields of work, chronologically listed, are:
1000 BCE to 1 BCE
* Baudhayana (fl. c. 800 BC) – Euclidean geometry, geometric algebra
* ...
and the son of legal scholar
Paul Johann Anselm Ritter von Feuerbach, and the brother of philosopher
Ludwig Feuerbach
Ludwig Andreas von Feuerbach (; 28 July 1804 – 13 September 1872) was a German anthropologist and philosopher, best known for his book '' The Essence of Christianity'', which provided a critique of Christianity that strongly influenced gene ...
. After receiving his doctorate at age 22, he became a professor of
mathematics at the
Gymnasium at
Erlangen
Erlangen (; East Franconian: ''Erlang'', Bavarian: ''Erlanga'') is a Middle Franconian city in Bavaria, Germany. It is the seat of the administrative district Erlangen-Höchstadt (former administrative district Erlangen), and with 116,062 inhab ...
. In 1822 he wrote a small book on mathematics noted mainly for a theorem on the
nine-point circle
In geometry, the nine-point circle is a circle that can be constructed for any given triangle. It is so named because it passes through nine significant concyclic points defined from the triangle. These nine points are:
* The midpoint of ea ...
, which is now known as
Feuerbach's theorem
In the geometry of triangles, the incircle and nine-point circle of a triangle are internally tangent to each other at the Feuerbach point of the triangle. The Feuerbach point is a triangle center, meaning that its definition does not depend on th ...
. In 1827 he introduced
homogeneous coordinates
In mathematics, homogeneous coordinates or projective coordinates, introduced by August Ferdinand Möbius in his 1827 work , are a system of coordinates used in projective geometry, just as Cartesian coordinates are used in Euclidean geometry. ...
, independently of
Möbius.
Works
* . ("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")
References
External links
*
*
Feuerbach's Theorem: a Proof*
{{DEFAULTSORT:Feuerbach, Karl Wilhelm
1800 births
1834 deaths
Writers from Jena
People from Saxe-Weimar
German Lutherans
19th-century German mathematicians
Geometers