∵EF∥AD∥BC
∴GE / GB = EF / BC HE / HA = EF / AD

∵AD = BC
∴GE / GB = HE / HA BR p>∴GE / BE = HE / AE

另外∵∠AEB =∠HEG

∴ΔAEB∽ΔHEG
∴∠ABE = ∠HGE

∴GH∥AB ∵EF∥AD∥BC
∴GE / GB = EF / BC HE / HA = EF / AD

∵AD = BC
∴GE / GB = HE / HA BR p>∴GE / BE = HE / AE

另外∵∠AEB =∠HEG

∴ΔAEB∽ΔHEG
∴∠ABE = ∠HGE

∴GH∥AB