y=cos2x+sin2x
=√2(√2/2cos2x+√2/2sin2x)
=√2(sinπ/4cos2x+cosπ/4sin2x)
=√2sin(2x+π/4)
周期为：2π/2=π
y=√3cosx+sinx
=2(√3/2cosx+1/2sinx)
=2*(sin(π/3)cosx+cos(π/3)sinx
=2*sin(x+π/3)
周期为：2π