首先,对于正余弦如Asin(nx+a)或者Acos(nx+a)的周期均为：2π/n
y=sinx+cosx
=√2[sinx*cos(π/4)+cosx*sin(π/4)]
=√2sin(x+π/4)
周期为:2π/1=2π
y=sin(nx+pai／8)
周期为:2π/n
y=1／2（cosx）平方
=1/2[(1+cos2x)/2]
=1/4(1+cos2x)
周期为:2π/2=π