( 1)∵AD//BC?
∴∠F=∠ 1
∫∠2 =∠ 1
∴∠2=∠F
∴AB=BF
∫AD+BC = AB,
∴AD+BC=BF
∴AD=CF
∠∠5 =∠6
∴δade≌δfce
∴DE=CE
(2) According to (1), BA=BF and EA=EF.
And BE=BE.
∴δabe≌δfbe
∴∠3=∠4