His eponymous curvature is the product of the principal curvatures of a surface, while his eponymous function is its own Fourier transform and is important in probability theory.  
Lemmas named for him include one that determines the angle that a tangent vector makes with a geodesic, while another states that a polynomial is irreducible over the integers if and only if it is irreducible over the rationals.  His eponymous curvature is the product of the principal curvatures of a surface, while his eponymous function is its own Fourier transform and is important in probability theory.  As a teenager he proved the law of quadratic reciprocity and the fundamental theorem of algebra.  FTP, name this mathematician who also developed the method of least squares and the normal probability distribution.
Lemmas named for him include one that determines the angle that a tangent vector makes with a geodesic, while another states that a polynomial is irreducible over the integers if and only if it is irreducible over the rationals.  
(Johann Friedrich) Karl Gauss