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



ProveIt! by Michael Ferraro <mferraro@balstaff.org>.
Copyright ©2010. All rights reserved.