Proof: Triangle Sum Theorem 3     
AFB = 60
BCD = 30
line AB line AD
line AB line DC
1. 
1. 
CDA = 90
60 + 30 + CDA = 180; 90 + CDA = 180
line AB line DC
AFB + BCD + CDA = 180
AFB = 60
line DC line AD
BCD = 30
line AB line AD



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