A928368712你好!解:过点E作EF∥AB∵EF∥AB∴∠B ∠BEF=180 (同旁内角互补)∴∠BEF=180-∠B∵∠BED=∠BEF ∠DEF∴∠BED=180-∠B ∠DEF∴∠BED ∠B=180 ∠DEF∵∠B ∠BED ∠D=360∴180 ∠DEF ∠D=360∴∠DEF ∠D=180∴EF∥CD (同旁内角互补,两直线平行)∴AB∥CD (平行于同一直线的两直线平行) 祝:学习进步!
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