f(x+2)=-1/f(x)
f(x+4)=-1/(f(x+2))=-1/(-1/f(x))=f(x)
f(x)是以4为周期的函数
f(105.5)=f(105.5-26*4)=f(1.5)
[f(x)偶函数]
=f(-1.5)=f(-1.5+4)=f(2.5)
[当2≤x≤3,f(x)=x]
=2.5