如何证明对角线长相等的梯形是等腰梯形

已知在梯形ABCD中,AD∥BC,AC = BD ；过点D作DE∥AC,交BC延长线于点E；因为,AD∥CE,DE∥AC,所以,ACED是平行四边形,可得：DE = AC = BD ,所以,∠DBE = ∠DEB = ∠ACB ；因为,在△ABC和△DCB中,AC = DB ,∠ACB = ∠DBC ...