Step 2: ∠DAB+∠DCB= 180 (diagonal complementation of quadrangles inscribed in a circle)

Step 3: ∠DAB+∠DAE= 180 (straight angle is 180).

Step 4: DAE = DAC (angle bisector)

Step 5: Therefore, ∠DBC=∠DCB, then DB=DC (the diagonal sides of an isosceles triangle are equal).