适用两类不同函数相乘
(在前的为u,在后为v)
∫ex2dx∫sinxxdx∫cosxxdx\begin{array}{l} \int e^{x^{2}} d x \\ \int \frac{\sin x}{x} d x \\ \int \frac{\cos x}{x} d x \end{array}∫ex2dx∫xsinxdx∫xcosxdx