已知函数f(x)=√3sin^2x+sinxcosx-√3/2(x∈R).(1)若x∈(0,π/2),求f (x)的最大值.

问题描述:

已知函数f(x)=√3sin^2x+sinxcosx-√3/2(x∈R).(1)若x∈(0,π/2),求f (x)的最大值.

这个简单。f(x)=√3sin2x+0.5sin2x-√3/2=(-√3+0.5)sin2x-√3/2 所以最大值为-3√3/2+1/2

f(x)=√3sin^2x+sinxcosx-√3/2
=√3(1-cos2x)/2+sin2x/2-√3/2
=(1/2)sin2x-(√3/2)cos2x
=sin(2x-π/3)
x∈(0,π/2)
2x-π/3∈[-π/3,2π/3]
所以
f(x)的值域为[-√3/2,1]
最大值为 1

f(x)=根号3sin^2x+sinxcosx-根号3/2
=sinxcosx-√3/2*(1-2sin²x)
=(1/2)sin2x-(√3/2)cos2x
=sin(2x)*cos(π/3)-cos(2x)sin(π/3)
=sin(2x-π/3)
如0

f(x)=√3/2*(1-cos2x)+1/2*sin2x-√3/2
=1/2*sin2x-√3/2*cos2x
=sin(2x-π/3)
00-π/3所以f(x)的最大值为1