在Rt△ABC中,∠BAC=90°,AD⊥BC
∠BAE=∠BDF=90
BE是∠ABC的平分线
∴∠ABE=∠DBF
∠ABE+∠AEB=90
∠DBF+∠DFB=90
∠AEB=∠DFB
∠DFB=∠AFE
∠AEB=∠AFE
AF=AE