求函数y=(cos x-2)/(cos x-1)的周期,
问题描述：
求函数y=(cos x-2)/(cos x-1)的周期,
答
y=[cosx-1-1]/(cosx-1)
=1-1/(cosx-1)
=1-1/(1-2sin^2(x/2)-1)
=1+1/(2*sin^2(x/2))
故其周期是 T=2π