In △DBE,
DB=BE
Hence, ∠DBE=∠DEB=x (I)
In △DAE,
DA=AE
Hence, ∠DAE=∠DEA=y (II)
Now, In △ABE,
∠ABE+∠BAE+∠AEB=180 (Sum of angles of triangle)
∠ABE+∠BAE+∠BED+∠DEA=180
x+x+y+y=180
x+y=90
∠DEB+∠DEA=90
∠AEB=90∘
Hence, ∠AEB=∠AEC=90∘
In △AEF,
Sum of angles = 180
∠AEF+∠EAF+∠EFA=180
∠AEF+∠EAF+90=180
∠AEF=90−∠EAF
We know, ∠AEC=90
∠AEF+∠FEC=90
90−∠EAF+∠FEC=90
or ∠EAF=∠FEC=∠CEG