∵四边形ABCD是正方形,
∴AB=BC=CD=AD,∠B=90°,∠ACB=∠BAC=45°. ∵正方形ABCD的周长为8cm, ∴AB=BC=CD=AD=2cm. ∵四边形EFBG是矩形, ∴EG=FB,FE=GB,EG∥FB,FE∥GB, ∴∠AFE=∠EGC=90°, ∴∠AEF=∠GEC=45°, ∴∠FAE=∠FEA,∠GEC=∠GCE, ∴AF=EF,GE=GC. ∵C矩形EFBG=EG+FE+FB+GB, ∴C矩形EFBG=AF+FB+GB+GC=AB+BC=2+2=4cm. 故答案为:4cm. |