已知函数f(x)=sin(2x+π3)+sin(2x-π3)+2cos2x-1,x∈R(1)求函数f(x)的最小正周期;(2)求函

2025-02-11 21:43:44
推荐回答(1个)
回答(1):


f(x)=sin2x×

1
2
+
3
2
cos2x+
1
2
sin2x?
3
2
cos2x+cos2x

=sin2x+cos2x
=
2
sin(2x+
π
4
)

(1∵0∴
T=
2
=π

(2)由f(x)可以看出函数f(x)的增区间为
2x+
π
4
∈[?
π
2
+2kπ,
π
2
+2kπ
]
即函数f(x)的增区间为:[-
8
+kπ,
π
8
+kπ
]k∈Z
(3)∵x∈[-
π
4
π
4
]
2x+
π
4
∈[?
π
4
4
]

根据正弦函数的增减区间可知:
当2x+
π
4
=-
π
4
时,f(x)min=-1;
当2x+
π
4
=
π
2
时f(x)max=