∵GF=GB
∴∠GFB=∠GBF
∵AF=BD
∴AF+FB=FB+BD
即AB=DF
∵∠A=∠D,∠GBF=∠GFB
∴△ABC≌△DFE(ASA)
∴BC=EF
∴BC-GB=EF-GF
即 CG=EG