Proof: Converse of Parallel Lines 4     
line ABCD
ECD = 140
ABF = 40
line BF line CE
1. 
1. 
FBC = FBC
ABC = ABF + FBC
FBC + BCE = FBC + BCE
140 = FBC
FBC + BCE = 140 + 40; FBC + BCE = 180
line ABCD
40 = BCE
ABF = 40
FBC and BCE are supplementary
180 = 40 + FBC
BCD = BCE + ECD
ECD = 140
ABC = 180
BCD = 180
line BF line CE
180 = BCE + 140



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