Thanks for your response.
My problem is it is a practical application and I don't know the center point, only 5 points on the curved surface of the object. I should have also mentioned the points are all the same in the z axis, it is only the position of the points in the x and y-axis which...
I have a curved surface which I know the (x,y and z) coordinates for 5 separate points on it and I was wondering how to determine the radius of this curved surface from the coordinates and then interpolate so that I can obtain points across the whole surface?
Many thanks.