Integral Calculus

While differential calculus deals with the determination of the derivative (absolute gradient) \( f'(x) \) of a given function f (x), integral calculus - starting from a given derivative function \( f'(x) \) - is interested in the underlying original function f (x). The original function is called the antiderivative, inverse derivative or primitive function. The return from the derivative function to the antiderivative is called integration.