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.
1 a constant or variable term in a function that determines the specific form of the function but not its general nature, as a in f (x) = ax, where a determines only the slope of the line described by f (x).  one of the independent variables in a set of parametric equations.