**Answer:**

AD = b units and AE = a units.

D(0, b), E(a, 0) and A(0, 0) lies on the circle. C is the centre.

The general equation of a circle:

(x – h)^{2} + (y – k)^{2} = r^{2} …(i)

(h, k) is the centre and r is the radius.

Putting A(0, 0) in (i)

(0 – h)^{2} + (0 – k)^{2} = r^{2}

The required equation is,