Integration by Parts
Integration by parts is a useful strategy for simplifying some integrals. It is based on the combination rule for differentiation and the general approach can be summarized by:
This technique is particularly appropriate for removing a linear term multiplying an exponential. For example, the integral
can be simplified by the identification
Then u can be differentiated and dv can be integrated.
The value of the integral is then
If a higher power term of x multiplies the exponential, then the process of integration by parts can be repeated to reduce the power term. Two stages are necessary to integrate a square term.
Three stages are necessary if the integrand has a cubic term, and so on.