y=(sinx+cosx+1)/(cosx+1)
=[2sin(x/2)cos(x/2)+2cos²(x/2)]/[2cos²(x/2)]
=[sin(x/2)+cos(x/2)]/cos(x/2)
=1+tan(x/2)
最小正周期=π/(1/2)=2π
最小正周期为2π.