Chapter 4 - Integrals - 4.3 The Fundamental Theorem of Calculus - 4.3 Exercises - Page 327: 1

They are inverse processes because one process undoes the other.

From the Fundamental Theorem of Calculus, $ \frac{d}{dx} \int f(x) = f(x) $. Therefore, taking the derivative of an integral will undo the integral, and similarly the other way around as well.