f(x)=3sinx^2+2根号3sinxcosx+5cosx^2
=3* (1-cos2x)/2+根号3sin2x+5* (1+cos2x)/2
=3/2-3/2cos2x+根号3sin2x+5/2+5/2cos2x
=4+cos2x+根号3sin2x
=4+2sin(2x+π/6)
T=2π/2=π
最大值=6
f(a)=5,即sin(2x+π/6)=1/2
∴a=0
所以tana=tan0=0
f(x)=3sinx^2+2根号3sinxcosx+5cosx^2
=3* (1-cos2x)/2+根号3sin2x+5* (1+cos2x)/2
=3/2-3/2cos2x+根号3sin2x+5/2+5/2cos2x
=4+cos2x+根号3sin2x
=4+2sin(2x+π/6)
T=2π/2=π
最大值=6
f(a)=5,即sin(2x+π/6)=1/2
∴a=0
所以tana=tan0=0