If a circle passes through the point (0, 0) (a, 0), (0, b) then find the coordinates of its centre.
We have a circle through the point A(0,0), B(a,0) and C(0,b). Clearly triangle is right angled at vertex A. So, the centre of the circle is the mid-point of hypotenuse BC which is (a/2,b/2)