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 names
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