




We write f(b)  f(a) as the sum of the difference of f over many little intervals x_{k}  x_{k1}
We apply the mean value theorem on each small interval
This yields, for some c_{k} in the kth interval for each k.
This is a Riemann sum for integrand f '(x), limits a and b, and variable of integration x, for any n.
By taking the limit as , we get