f(x)=向量m*向量n=(sinwx+coswx,√3coswx)(coswx-sinwx,2sinwx)=
=(cos^2wx-sin^2wx,2√3sinwxcoswx)=cos^2wx-sin^2wx + 2√3sinwxcoswx=
=con2wx+√3sin2wx=2[sinπ/6con2wx+conπ/6sin2wx]=2sin(2wx+π/6),
f(x)=2sin(2wx+π/6)的对称轴是：x1=π/2-π/6,x2=2w+π/2-π/6,
w>0,f(x)相邻两个对称轴间的距离大于等于π/2,
即 x2-x1=2w≥π/2,w≥π/4.