1、∵ B是EC的中点,
∴ BE = BC.
∵ ∠ABE = ∠DBC,
∴∠ABE + ∠ABD = ∠DBC + ∠ABD,
即∠DBE = ∠ABC.在△DEB和△ACB中,
∵ ∠DBE = ∠ABC,∠D = ∠A,
BE = BC,
∴ △DEB ≌ △ACB( AAS).
∴DE = AC.
2、∵ CD ⊥ AB,EF ⊥ AB,
∴ ∠CDB = ∠EFA = 90°,
∵ AD = BF,
∴ AD + DF = BF + DF,即AF = BD.在△CBD和△EAF中,
∵ CD = EF, ∠CDB = ∠EFA,BD = AF,
∴△CBD ≌ △EAF(SAS).
∴∠A = ∠B.
3、∵ ∠AFB = ∠AEC,∠B = ∠C,AB = AC,
∴ △ABF ≌ △ACE(AAS).
∴ ∠BAF = ∠CAE.
∴ ∠BAF - ∠EAF = ∠CAE - ∠EAF,即∠BAE = ∠CAF.