∵∠BAD=60°,AB=AD∴△ABD是等边三角形∴BD=AD,∠ADB=60°∵∠BCD=120°∴∠DCE=60°∵CD=CE∴△CDE是等边三角形∴CD=DE,∠CDE=60°∴∠CDE+∠BCD=∠ADB+∠BCD∴∠BDE=∠ADC∵AD=BD,CD=DE∴△ACD≌△BED∴AC=BE=BC+...