作 BE的延长线交CD的延长线于F∵CE是∠BCD的平分线∴∠BCE=∠FCE∵AB∥CD∴∠F=∠FBA∵BE是∠ABC的平分线∴∠ABF=∠FBC∴∠FBC=∠F又CE=CE∴△FCE≌△BCE∴EF=BE，BC=FC又∠DEF=∠AEB，EF=BE，∠F=∠FBA∴△AEB≌△DEF∴AE=ED
