The fundamental theorem relates accumulation and rate of change by stating that if F′(x)=f(x), then the accumulated area A(x) from a fixed point a to x is given by A(x)=F(x)−F(a). It shows that differentiation and integration are inverse processes: the derivative of the accumulation function A(x) recovers the integrand f(x), and antiderivatives allow the evaluation of definite integrals.
Conditions: The function f is continuous.; F is an antiderivative of f (i.e., F′=f).