Sub-scenario:

(1) If two sides with a side length of A are not adjacent (opposite), A becomes larger from 0 until the other four sides become larger.

Square, where a is the diagonal of the square, a &；; sup2= 2 & ampsup2+2 & amp； Sup2, radical number 2 with a=2,

So a ∈ (0 0,2 root number 2);

(2) If two sides with side length A are adjacent, A increases from 2/2= 1 until the other four sides are in the same plane.

When a&; sup2= 1。 The square of sup2+ radical number 3+2 & sup2 = radical number 3 of 8+4 = (square root of 6+radical number 2)&; Sup2, the square root of a =+radical number 2.

So a∈( 1, the square root of 6+radical sign 2)

Comprehensive ① ② A belongs to (square root of 0,6+radical number 2).