When substitution can't crack an integral, it's often because the integrand is a product of two unrelated functions—like a polynomial and an exponential—or a bundle of trigonometric functions. This chapter gives you two new tools that handle these cases: integration by parts, which turns one product into another (hopefully simpler) product, and a set of strategies for rewriting powers and products of sine, cosine, secant, and tangent into forms you can integrate.