AB=ac ED=EC
∠B=∠C ∠1=∠B
DE‖AB FB=FD
∠B=∠2
∠袭芦2=∠C AF+FB=AF+FD=AB
DF‖AC EC+AE=AE+ED=AC
∠拍行带1=∠C AB+AC=6
∠1=∠B 四边形AFDE=6+6=12
∠带碧2=∠C
注; ∠1=∠FDB ∠2=∠EDC
DF‖AC => DF/橡知AC=BF/梁悉消AB => BF=DF
DE‖AB => DE/AB=CE/AC => DE=CE
周陆贺长AF+FD+DE+ED = AF+BF+CE+AE = AB+BC = 12