已知函数fx=根号2sin(2x+3分之π)的单调性和最小正周期,还有在[0,,2分之π】的值域
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解决时间 2021-02-09 10:42
- 提问者网友:你独家记忆
- 2021-02-08 22:50
详细步骤!!!!因为很急!所以谢谢!
最佳答案
- 五星知识达人网友:酒醒三更
- 2021-02-09 00:01
f(x)=√2sin(2x+π/3)
=√2sin(2x+2π+π/3)
=√2sin[2(x+π)+π/3]
∴最小正周期=π
∵2kπ-π/2<2x+π/3<2kπ+π/2
即 kπ-5π/12<x<kπ+π/12
∴f(x)在kπ-5π/12<x<kπ+π/12单增
∵2kπ+π/2<2x+π/3<2kπ+3π/2
即 kπ+π/12<x<kπ+7π/12
∴f(x)在kπ+π/12<x<kπ+7π/12单减
∵0<x<π/2
即 2π/3<2x+π/3<5π/3
f(x)在2x+π/3∈(2π/3,3π/2)递减,在2x+π/3∈(3π/2,5π/3)递增,
在2x+π/3=2π/3 函数值=√6/2,最大
在2x+π/3=3π/2时,函数值最小=-√2
∴函数在[0,,2分之π】的值域:[-√2, √6/2]
=√2sin(2x+2π+π/3)
=√2sin[2(x+π)+π/3]
∴最小正周期=π
∵2kπ-π/2<2x+π/3<2kπ+π/2
即 kπ-5π/12<x<kπ+π/12
∴f(x)在kπ-5π/12<x<kπ+π/12单增
∵2kπ+π/2<2x+π/3<2kπ+3π/2
即 kπ+π/12<x<kπ+7π/12
∴f(x)在kπ+π/12<x<kπ+7π/12单减
∵0<x<π/2
即 2π/3<2x+π/3<5π/3
f(x)在2x+π/3∈(2π/3,3π/2)递减,在2x+π/3∈(3π/2,5π/3)递增,
在2x+π/3=2π/3 函数值=√6/2,最大
在2x+π/3=3π/2时,函数值最小=-√2
∴函数在[0,,2分之π】的值域:[-√2, √6/2]
全部回答
- 1楼网友:舍身薄凉客
- 2021-02-09 01:10
2x。=2π,x。=π
最小正周期: π
主值单调递增区间:
-π/2<=2x+3分之π<=π/2
-5π/6<=2x<=π/6
-5π/12<=x<=π/12
主值单调递减区间:
。。。
在[0,,2分之π】区间
3分之π<=π+3分之π
则 -根号3<=f(x)<=2
- 2楼网友:低音帝王
- 2021-02-09 00:41
f(x)= sin^2(2x+π/4) + √3 cos^2(2x)
= {sin2xcosπ/4+cos2xsinπ/4}^2 + √3 cos^2(2x)
= 1/2(sin2x+cos2x)^2 + √3 cos^2(2x)
= 1/2(1+2sin2xcos2x) + √3 * (cos4x+1)/2
= 1/2 + 1/2sin4x +√3/2 cos4x + √3/2
= sin4xcosπ/3 + cos4xsinπ/3 + (1+√3)/2
= sin(4x+π/3) + (1+√3)/2
最小正周期=2π/4=π/2
当4x+π/3∈(2kπ+π/2,2kπ+3π/2),其中k∈z时单调减
单调减区间:x∈(kπ/2+π/24,kπ/2+7π/24),其中k∈z
若x∈【-π/6,π/6】
4x+π/3∈(-π/3,π)
4x+π/3=-π/3,x=-π/6时,函数有最小值f(x)min=sin(-π/3) + (1+√3)/2 = -√3/2+(1+√3)/2 = 1/2
4x+π/3=π/2,x=π/24时,函数有最大值f(x)max=sin(π/2) + (1+√3)/2 = 1+(1+√3)/2 =(3+√3)/2
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