f(x)= √3sinx+cosx
=2[(√3/2)sinx+(1/2)cosx]
=2sin(x+π/6)
(1) 最小正周期T=2π/1=2π
∵sin(x+π/6)≤1
∴f(x)最大值=2
(2) f(α)=2sin(α+π/6)=2/3
sin(α+π/6)=1/3
cos(2α+π/3)=cos[2(α+π/6)]
=1-2[sin(α+π/6)]^2
=1-2*(1/3)^2
=1-2/9
=7/9