已知y=sinx1+cosx,x∈(0,π).當(dāng)y'=2時(shí),x等于( ) A.π3 B.23π C.π4 D.π6
已知
y=,x∈(0,π).當(dāng)y'=2時(shí),x等于( ?。?br/>A.
B.
πC.
D.
優(yōu)質(zhì)解答
由
y=,得:
y′=(sinx)′(1+cosx)?sinx(1+cosx)′ |
(1+cosx)2 |
=
cosx+cos2x+sin2x |
(1+cosx)2 |
=
==2.
所以
cosx=?,因?yàn)閤∈(0,π),所以
x=π.
故選B.
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