过O作OM∥BC,交CD于M∵平行四边形ABCD中,AC,BD交于点O∴BO＝DO＝BD/2∵OM∥BC∴OM/BC＝OD/BD＝1/2∵BC＝6∴OM＝3同理可证CM＝CD/2＝AB/2＝4/2＝2∵OM∥BC∴CF/OM＝CE/CM∵CE=2∴CF/OM＝2/4＝1/2∴CF＝OM/2＝3/2
