His namesake points are the midpoints of the line segments that join a triangle's vertices to its orthocenter.  His namesake squares are arrays composed of Latin Squares.  His namesake characteristic is 0 only for the Klein bottle and the torus.  Along with Lagrange, he names a differential equation involved in the calculus of variations.  In 3-dimensional space, his rotation theorem says that any rotation can be described with the matrix formulation of his namesake angles.  FTP, give this namesake of a formula that relates the vertices, edges and faces of a polyhedron
His namesake points are the midpoints of the line segments that join a triangle's vertices to its orthocenter.  His namesake squares are arrays composed of Latin Squares.  His namesake characteristic is 0 only for the Klein bottle and the torus.  Along with Lagrange, he names a differential equation involved in the calculus of variations.  In 3-dimensional space, his rotation theorem says that any rotation can be described with the matrix formulation of his namesake angles.  FTP, give this namesake of a formula that relates the vertices, edges and faces of a polyhedron and a constant equal to approximately .577, who also happens to be a Swiss mathematician.
His namesake points are the midpoints of the line segments that join a triangle's vertices to its orthocenter.  
Leonard Euler