(1) From the meaning of the question: the coordinates of point B (|OA|, |OC|), OA=OC, then 1=|OA|? |OC|，OA= 1，

The side length of a square OABC is 1.

(2) Since the side length of the square ADEF is a, then E( 1+a, a),

Substituting the inverse proportional function y = 1x (x > 0) gives: 1=( 1+a)a, and a > 0.

Solution: A =- 1+52.