Integration is often introduced as the reverse process to differentiation, and has wide applications, for example in finding areas under curves and volumes of solids. This section explains what is meant by integration and provides many standard integration techniques.

# Integration by parts

A special rule, integration by parts, can often be used to integrate the product of two functions. It is appropriate when one of the functions forming the product is recognised as the derivative of another function. The result still involves an integral, but in many cases the new integral will be simpler than the original one. Video tutorial 26 mins.