This man names an approximation that includes an error term of a Bernoulli number-containing integral, used to approximate infinite series. He names a numerical process used to find solutions to ordinary differential equations. The number of positive integers less than and coprime to n is his totient function. This man found that all convex polyhedrons have the same value for the sum of their vertices, edges, and faces, his so-called "characteristic." That finding, as well as his negative resolution of the Seven Bridges of KÃ¶nigsberg problem, 
This man names an approximation that includes an error term of a Bernoulli number-containing integral, used to approximate infinite series. He names a numerical process used to find solutions to ordinary differential equations. The number of positive integers less than and coprime to n is his totient function. This man found that all convex polyhedrons have the same value for the sum of their vertices, edges, and faces, his so-called "characteristic." That finding, as well as his negative resolution of the Seven Bridges of KÃ¶nigsberg problem, formed the basis for topology. For 10 points, name this Swiss mathematician whose namesake identity relates e, pi, i, and 1.
This man names an approximation that includes an error term of a Bernoulli number-containing integral, used to approximate infinite series.
Leonhard Euler 