f(x)=3√3sinxcosx+2cos²x+(sin²x+2cos²x)-(5/2)
=(3√3/2)sin2x+(3/2)(cos2x+1)-(3/2)
=3[(√3/2)sin2x+(1/2)cos2x]
=3sin(2x+π/6)
1、x∈[π/6,π/2]
则:2x+π/6∈[π/2,7π/6]
则:f(x)∈[-3/2,3]
2、f(a)=3sin(2a+π/6)=3,则:a=π/6,则:f(a-π/12)=f(π/12)=3sin(π/3)=3√3/2
f(x)=3√3sinxcosx+2cos²x+(sin²x+2cos²x)-(5/2)
=(3√3/2)sin2x+(3/2)(cos2x+1)-(3/2)
=3[(√3/2)sin2x+(1/2)cos2x]
=3sin(2x+π/6)
1、x∈[π/6,π/2]
则:2x+π/6∈[π/2,7π/6]
则:f(x)∈[-3/2,3]
2、f(a)=3sin(2a+π/6)=3,则:a=π/6,则:f(a-π/12)=f(π/12)=3sin(π/3)=3√3/2