A student of Gauss at Göttingen, and Dirichlet [DEE-reech-lay] at Berlin, in his doctoral thesis, he described the conditions needed for a function to be integrable. A famous unsolved problem lies in finding the roots of his 
A student of Gauss at Göttingen, and Dirichlet [DEE-reech-lay] at Berlin, in his doctoral thesis, he described the conditions needed for a function to be integrable. A famous unsolved problem lies in finding the roots of his zeta function. For 10 points—name this German mathematician, who invented a non- Euclidean geometry, whose "sums" are taught to calculus students as a method of numerical approximation of an integral.
A student of Gauss at Göttingen, and Dirichlet [DEE-reech-lay] at Berlin, in his doctoral thesis, he described the conditions needed for a function to be integrable.
Georg Friedrich Bernhard {Riemann}