解由f(x+2)=1/f(x)
得f(x+4)
=f(x+2+2)
=1/f(x+2)
=1/[1/f(x)]
=f(x)
故函数的周期T=4
故f(5.5)
=f(5.5-8)
=f(-2.5)
=f(2.5)
=2.5