Polynomial Method in Computer Graphics
The first method defines a circle with the second-order polynomial equation as shown in fig:
y2=r2-x2
Where x = the x coordinate
y = the y coordinate
r = the circle radius
With the method, each x coordinate in the sector, from 90° to 45°, is found by stepping x from 0
to 
& each y coordinate is found by evaluating 
2-x2 for each step of x.
Algorithm:
Step1: Set the initial variables
r = circle radius
(h, k) = coordinates of circle
center x=o
I= step size
xend=
Step2: Test to determine whether the entire circle has been scan-converted. If x >xend then stop.
Step 3: Compute y=
Step4: Plot the eight points found by symmetry concerning the center (h, k) at the current (x, y) coordinates.
Plot (x + h, y +k) Plot (-x + h, -y + k) Plot (y + h, x + k)
Plot (-y + h, -x + k) Plot (-y + h, x + k) Plot (y + h, -x + k)
Plot (-x + h, y + k) Plot (x + h, -y + k)
Step5: Increment x =x + i
Step6: Go to step (ii).