(a-a/a-1)÷a²+a/a-1=1/(a-1)*[(a-2)/a+a]
=1/(a-1)*[(a-1)(a+2)/a]
=1+2/a
a=根号2sin45°+2=1+2=3
(a-a/a-1)÷a²+a/a-1=1+2/a
=1+2/3
=5/3