( 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