题目内容
求下列函数的导数
(1)y=sinxcosx
(2)y=x2ex
(3)y=(
+1)(
-1)
(4)y=sin
(1-2cos2
)
(1)y′=(sinx)′cosx+sinx(cosx)′
=cosxcosx-sinxsinx
=cos2x.
(2)y′=(x2)′ex+x2(ex)′
=2x·ex+x2·ex
=(x2+2x)ex.
(3)∵y=1-
+
-1
=-x
+x![]()
∴y′=-
x
-
x![]()
=-
x
(1+x-1)=-
(1+
).
(4)∵y=sin
(-cos
)=-
sinx
∴y′=(-
sinx)′=-
cosx.
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