证明设函数为y=f（wx）则令F(x)=f（wx）则F(x+2π/w)=f（w（x+2π/w））=f（wx+2π）=f（wx）=F(x)即F(x+2π/w)=F(x)则F(x)是周期为2π/w即函数y=f（wx）周期为2π/w.
