题目内容
已知函数f(x)=-
sin2x+sinxcosx
(I)求函数f(x)的最小正周期;
(II)求函数f(x)在x∈[0,
]的值域.
| 3 |
(I)求函数f(x)的最小正周期;
(II)求函数f(x)在x∈[0,
| π |
| 2 |
f(x)=-
sin2x+sinxcosx
=-
×
+
sin2x
=
sin2x+
cos2x-
=sin(2x+
)-
,
(I)T=
=π
(II)∴0≤x≤
,
∴
≤2x+
≤
,
∴-
≤sin(2x+
)≤1,
所以f(x)的值域为:[-
,
]
| 3 |
=-
| 3 |
| 1-cos2x |
| 2 |
| 1 |
| 2 |
=
| 1 |
| 2 |
| ||
| 2 |
| ||
| 2 |
=sin(2x+
| π |
| 3 |
| ||
| 2 |
(I)T=
| 2π |
| 2 |
(II)∴0≤x≤
| π |
| 2 |
∴
| π |
| 3 |
| π |
| 3 |
| 4π |
| 3 |
∴-
| ||
| 2 |
| π |
| 3 |
所以f(x)的值域为:[-
| 3 |
2-
| ||
| 2 |
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