∴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.