Question

已知如图AB平行于CD,AB等于FC,角DCB加角ECF等于180度,求证AC等于EF

Answer 1

ab//cd

则∠ABC+∠BCD=180°

又∠BCD+∠ECF=180°

则∠ABC=∠ECF

△ABC和△ECF中,AB=EC,∠ABC=∠ECF,BC=CF

则△ABC≌△ECF

则AC=EF