A. \( - x\cos x - \sin x + C\)
B. \(x\cos x - \sin 2x + C\)
C. \( - x\cos x + \sin x + C\)
D. \(x\cos x - \sin x + C\)
C
Đặt \(\left\{ {\begin{array}{*{20}{l}}{u = x \Rightarrow du = dx}\\{dv = \sin xdx \Rightarrow v = {\rm{\;}} - \cos x}\end{array}} \right..\)
\(\begin{array}{*{20}{l}}{ \Rightarrow \int {x\sin xdx = {\rm{\;}} - x\cos x - \int { - \cos xdx} } }\\{{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} = {\rm{\;}} - x\cos x + \int {\cos xdx} }\\{{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} = {\rm{\;}} - x\cos x + \sin x + C}\end{array}\)
Chọn C.
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