已知函数f(x)=cos(2x-π3)+2sin(x-π4)sin(x+π4)(1)求函数f(x)的最小正周期和图象的对称轴

2025-02-14 06:16:31
推荐回答(1个)
回答1:

(1)∵sin(x+
π
4
)=cos(
π
4
-x)=cos(x-
π
4

∴f(x)=cos(2x-
π
3
)+2sin(x-
π
4
)sin(x+
π
4
)=cos(2x-
π
3
)+sin(2x-
π
2

=
1
2
cos2x+
3
2
sin2x-cos2x=
3
2
sin2x-
1
2
cos2x=sin(2x-
π
6

因此,函数f(x)的最小正周期T=
2

令2x-
π
6
=
π
2
+kπ
(k∈Z),可得x=
π
3
+
1
2
(k∈Z),
∴函数f(x)图象的对称轴方程为x=
π
3
+
1
2
(k∈Z).
(2)由(1)得f(α)=sin(2α?
π
6
)=
3
5

f(α+
π
12
)
=sin2α=sin[(2α?
π
6
)+