AB=CD，∠A=∠C

∴△ABE≌△CDF(ASA)

∴AE=CF

4、BE = CF

Then BE+EF+EF+CF

∴BF=CE

BF = CE，∠A=∠D，∠B=∠C

∴△ABF≌△DCE(AAS)

∴AB=DC