问题 选择题
下列运算正确的是(  )
A.[cos(1-x)]′=-sin(1-x)B.(eπx)′=eπx+eπ
C.(ax)′=xax-1D.(ln
1
x
)′=-
1
x
答案

[cos(1-x)]=-sin(1-x)•(1-x)=sin(1-x);

(eπx)=eπ

(ax=axlna;

(ln

1
x
)=x•(
1
x
)=x•(-
1
x2
)=-
1
x

故选D.

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