∵ABCD是平心四边形∴AB＝DC AD∥BC ∠A＝∠C ∠ABC＝∠ADC∵DF平分∠ADC BE平分∠ABC∴∠EBC＝½∠ABC ∠ADF＝½∠ADC∴∠ADF＝∠EBCEBFD是∴EBFD是平行四边形∵BD⊥EF（对角线互相垂直的平行四边形是菱形）∴EBFD是菱形
