已知锐角△ABC中内角A、B、C的对边分别为a、b、c,且sin2A+sin2B=sin2C+sinAsinB.(1)求角C的值;(2)

2025-01-19 10:23:42
推荐回答(1个)
回答1:

(1)∵sin2A+sin2B=sin2C+sinAsinB
∴由正弦定理化简已知的等式得:a2+b2=c2+ab,即a2+b2-c2=ab,
∴cosC=

a2+b2?c2
2ab
=
1
2

∵0<C<
π
2
,∴C=
π
3

(2)f(x)=sin(ωx?
π
6
)?cosωx
=
3
sin(ωx?
π
3
)

∵f(x)图象上相邻两最高点间的距离为π,
ω
=π
,∴ω=2,∴f(A)=
3
sin(2A?
π
3
)

∵C=
π
3
,B=
3
?A
,0<A<
π
2
,0<B<
π
2

π
6
<A<
π
2
,∴0<2A-
π
3
3

0<sin(2A?
π
3
)≤1

∴0<f(A)≤
3