Calculus of variations is a field of
mathematical analysis that deals with maximizing or minimizing
functionals, which are
mappings from a set of
functions to the
real numbers. Functionals are often expressed as
definite integrals involving functions and their
derivatives. The interest is in
extremal functions that make the functional attain a maximum or minimum value – or
stationary functions – those where the rate of change of the functional is zero.