y=sin x／2 ＋（√3）cos x／2
=2sin(1/2*sinx/2+cos x／2*√3/2)
=2sin(sinx/2*cosπ/3+cos x／2*sinπ/3)
=2sin(x/2+π/3)
令x/2+π/3=kπ+π/2,则x=2kπ+π/3
令k=0,x=π/3就是一条对称轴 .（它的对称轴有无数多条.）