Kelly's story is truly inspirational. Kelly has shown that pure determination, dedication and hard work can and does change a person's life. At Life Leisure we have loved being part of Kelly's journey.
In calculus (a branch of mathematics), a differentiable function of one real variable is a function whose derivative exists at each point in its domain.
In the calculus of variations, a field of mathematical analysis, the functional derivative (or variational derivative) relates a change in a functional to a change in a function on which the functional depends.