# Klein, Christian Felix (1849–1925)

Felix Klein was a German mathematician noted for his work on non-Euclidean
geometry, the connections between geometry and group theory, and the theory of functions. His Erlangen Programm (1872) for unifying
the diverse forms of geometry through the study of equivalence in transformation
groups was profoundly influential, especially in the United States, for
over 50 years. In his *Lectures on the Icosahedron and the Solution of
Equations of the Fifth Degree* (1884, tr. 1888) he showed how the rotation
groups of regular solids could be applied to the solution of difficult algebraic
problems. Klein was professor of mathematics successively at the University
of Erlangen, the Technical Institute, Munich, and the universities of Leipzig
and Göttingen, and was a prolific writer and lecturer on the theory, history,
and teaching of mathematics.