(2) As shown in the figure: (BD or AC is diagonal, E and F are on AD and BC, and EF vertically divides BD or AC).

Solution: Let the length of line segment ED be x, as shown in the figure.

The quadrilateral BFDE is a diamond.

∴ ED=BE=x

And ∵ AB=3, AD=4 in the rectangular ABCD.

∴ AE=4-x

In Rt△ABE, AE 2 +AB 2 =BE 2.

∴

Solution: x=, ∴ ED=?

∴

(3) Solution: As shown in Figure ∵ Folding ∴DF=EF Let the length of the line segment DF be X, then EF = X.

? ∫ad = 3 ∴af=3-x

? Point E is the midpoint of AB, and AB=2.

? ∴

In Rt△AEF, there are

∴

Solution: x=, ∴AF=?

In rectangular ABCD, due to folding in half,

∴∠D=∠FEM=90 .？

∴∠ 1+∠2=90 。 ?

∠∠A =∠B = 90。

∴∠ 1+∠3=90 。 ?

∴∠2=∠3

∴ ∽ ,

∴

∴BM=

∴

?

?