已知函数f(x)=sinxcosx+3cos2x-32(x∈R).(1)写出f(x)的最小正周期及最大值;(2)求f(x)的增

2025-12-14 07:12:47
推荐回答(1个)
回答1:

由题意得,f(x)=sinxcosx+

3
cos2x-
3
2

=
1
2
sin2x+
3
(1+cos2x)
2
?
3
2

=
1
2
sin2x+
3
2
cos2x
=sin(2x+
π
3
)

(1)f(x)的最小正周期T=
2
=π,最大值是1;
(2)由?
π
2
+2kπ≤2x+
π
3
π
2
+2kπ
(k∈Z)得,
?
12
+kπ≤x≤
π
12
+kπ
,k∈Z
所以函数f(x)的单调递增区间为[?
12
+kπ,
π
12
+kπ]
(k∈Z).