This is just here as a test because I lose it
Term information
definition
In calculus of variations, the Euler-Lagrange equation for the action of the system. In classical mechanics, it is equivalent to Newton's laws of motion, but it has the advantage that it takes the same form in any system of generalized coordinates, and it is better suited to generalizations (see, for example, the "Field theory" section below). source: http://en.wikipedia.org/wiki/Euler-Lagrange_equations