求下列函数的导数:(1)y=(1-x)(1+1x);(2)y=lnxx;(3)y=tanx;(4)y=xe1-cosx

2025-01-31 22:59:47
推荐回答(1个)
回答1:

(1)∵y=(1-
x
)(1+
1
x
)=
1
x
-
x
=x?
1
2
?x
1
2

∴y′=(x-
1
2
)′-(x
1
2
)′=-
1
2
x-
3
2
-
1
2
x-
1
2

(2)y′=(
lnx
x
)′=
(lnx)′x?x′lnx
x2
=
+f(1
x
?x?lnx,x2)
=
1?lnx
x2

(3)y′=(
sinx
cosx
)′=
(sinx)′cosx?sinx(cosx)′
cos2x

=
cosxcosx?sinx(?sinx)
cos2x
=
1
cos2x

(4)y′=(xe1-cosx)′=e1-cosx+x(e1-cosx)′
=e1-cosx+x[e1-cosx?(1-cosx)′]
=e1-cosx+xe1-cosx?sinx
=(1+xsinx)e1-cosx