Proof: because EF bisects AD vertically.

So AE=ED, AF=DF, EF=EF.

So the triangle FAE is equal to the triangle FDE.

So the FAE angle is equal to the FDE angle

∠B= angle FDE- bad angle

∠CAF= angle FAD- angle CAD

Because AD is the bisector of ∠BAC.

So the angle is not good = angle CAD

So ∠B=∠CAF.

2

I don't want to write the process, give me an idea.

Triangle ADE is equal to triangle ADF(HL)

So DE=DF

So the triangle DEB is equal to the triangle DFC(AAS).

So angle B= angle C.

△ABC is an isosceles triangle.