已知函数f(x)=4cosxsin(x+π6)-1(1)求f(x)的最小正周期;(2)在△ABC中,角A所对的边为a,且f(

2025-02-25 01:32:51
推荐回答(1个)
回答1:

(Ⅰ)∵f(x)=4cosxsin(x+
π
6
)?1

=4cosx(
3
2
sinx+
1
2
cosx)?1

=
3
sin2x+2co
s
x?1

=
3
sin2x+cos2x

=2sin(2x+
π
6
)

∴f(x)的最小正周期为T=
2
π.
(Ⅱ)∵f(A)=2sin(2A+
π
6
)=2

所以 sin(2A+
π
6
)=1

又∴∵0<A<π,所以
π
6
<2x+
π
6
13π
6

∴2A+
π
6
=
π
2
,即A=
π
6

由正弦定理
a
sinA
=2R

∴R=1;
∴S△ABC=πR2=π.