已知函数f(x)=根号3sin(wx+φ)++(w>0,-π/2x=(π-2φ)/4=π/3==>φ=-π/6
∴f(x)=√3sin(2x-π/6)
(2)解析：设f(a/2)=√3/4,(π/6＜a＜2π/3)
f(a/2)=√3sin(a-π/6)=√3/4
sin(a-π/6)=sina*√3/2-cosa*1/2=1/4
∴√3sina-cosa=1/2
与sin^2a+cos^2a=1联立
解得sina=(√3+√15)/8
∴cos(a+3π/2)=sina=(√3+√15)/8