According to the meANing of the question: AM=AN and because m is the midpoint of arc AC, we can know that arc MC= arc AM= arc an. Then because of the arc length, etc.:
∠MAC=∠AMN. So AF=MF.
And ∠ MAC+∠ MEA = 90, ∠ AMN+∠ FME = 90. Available: ∠MEA=∠FME. Then MF=FE.
Available: AF=MF=FE. that is
:AF=EF .