∴AE∥CD,AE=CD，

EA = BA，

∴AB∥CD,AB=CD，

∴ quadrilateral ABCD is a parallelogram,

∴ad=bc；

(2) Solution: When ∠ e = 45, the quadrilateral ABCD is a square.

Quadrilateral ACDE is a parallelogram,

∴AC=DE，

BD = DE，

∴AC=DE，

∴? ABCD is rectangular,

BD = DE，

∴∠E=∠EBD=45，

∴∠BDE=90，

∫AC∑DE，

∴∠AFB=∠BDE=90，

∴AC⊥BD，

∴ quadrilateral ABCD is a square.