Ta có \(\int {f\left( x \right)dx} = \int {x\sin xdx} \)
Đặt \(\left\{ {\begin{array}{*{20}{c}}{u = x}\\{dv = \sin xdx}\end{array}} \right. \Leftrightarrow \left\{ {\begin{array}{*{20}{c}}{du = dx}\\{v = - \cos x}\end{array} \Rightarrow \int {x\sin xdx = - x\cos x} + \int {\cos xdx = - x\cos x + \sin x + C} } \right.\)