题目
5.y=e^-xcos(3-x)的微分为（）A. dy=e^-xcos(3-x)dxB. dy=e^-x[sin(3-x)-cos(3-x)]dxC. dy=e^-xsin(3-x)dxD. dy=e^-x[sin(3-x)+cos(3-x)]dx
5.$y=e^{-x}\cos(3-x)$的微分为（）
A. $dy=e^{-x}\cos(3-x)dx$
B. $dy=e^{-x}[\sin(3-x)-\cos(3-x)]dx$
C. $dy=e^{-x}\sin(3-x)dx$
D. $dy=e^{-x}[\sin(3-x)+\cos(3-x)]dx$
题目解答
答案
B. $dy=e^{-x}[\sin(3-x)-\cos(3-x)]dx$