CE=CF,BF=DE-------------------------------------------------------证明：根据条件：梯形ABCD中,AB//DC,AD=DC=CB可知：梯形ABCD是等腰梯形,∠A=∠B又∠A=∠CDE∴∠B=∠CDE由CE⊥AD及CF⊥AB可得∠CED=∠CFB=90°结...