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



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