∴DC=BA,DC//BA,∠CDB=∠ABD
Points g and h are on the extension lines of BA and DC, respectively, and AG=CH.
∴DH=BG,∠HDB=∠GBD=∠CDB=∠ABD
BE = DF,∠HDB=∠GBD,BG=DH
∴△GBE≌△DHF
∴GE=HF,∠GEB=∠DFH
∴∠GEF=∠HFE
∴GE‖FH
∴GE=FH,GE‖FH
A quadrilateral with one side parallel and equal is a parallelogram.
∴ Quadrilateral GEHF is a parallelogram.