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.