Problemddx(xcosx)\frac{d}{dx}(x \cos x)dxd(xcosx)分步解答套用 (fg)′=f′g+fg′(fg)' = f'g + fg'(fg)′=f′g+fg′,其中 f=xf = xf=x、g=cosxg = \cos xg=cosx。f′=1f' = 1f′=1,g′=−sinxg' = -\sin xg′=−sinx。结果:cosx−xsinx\cos x - x\sin xcosx−xsinx。答案cos(x)−xsin(x)\cos(x) - x\sin(x)cos(x)−xsin(x)想解其他题?打开 derivative 求解器 →相关例题/solve/calculus/derivative-of-cos-x延伸阅读/blog/chain-rule-mastery