The second method of defining a circle makes use of polar coordinates as shown in fig:

            x=r cos θ             y = r sin θ
Where θ=current angle
r = circle radius
x = x coordinate
y = y coordinate

By this method, θ is stepped from 0 to  & each value of x & y is calculated.

Exception Handling in Java - Javatpoint

Algorithm:

Step1: Set the initial variables:

            r = circle radius
            (h, k) = coordinates of the circle center
                i = step size
            θ_end=
            θ=0

Step2: If θ>θ_endthen stop.

Step3: Compute

            x = r * cos θ            y=r*sin?θ

Step4: Plot the eight points, found by symmetry i.e., 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 θ=θ+i

Step6: Go to step (ii).

Program to draw a circle using Polar Coordinates:

1. #include <graphics.h>  
2. #include <stdlib.h>  
3. #define color 10  
4. void eightWaySymmetricPlot(int xc,int yc,int x,int y)  
5. {  
6.     putpixel(x+xc,y+yc,color);  
7.     putpixel(x+xc,-y+yc,color);  
8.     putpixel(-x+xc,-y+yc,color);  
9.     putpixel(-x+xc,y+yc,color);  
10.     putpixel(y+xc,x+yc,color);  
11.     putpixel(y+xc,-x+yc,color);  
12.     putpixel(-y+xc,-x+yc,color);  
13.     putpixel(-y+xc,x+yc,color);  
14. }  
15. void PolarCircle(int xc,int yc,int r)  
16. {  
17.     int x,y,d;  
18.     x=0;  
19.     y=r;  
20.     d=3-2*r;  
21.     eightWaySymmetricPlot(xc,yc,x,y);  
22.     while(x<=y)  
23.     {  
24.         if(d<=0)  
25.         {  
26.             d=d+4*x+6;  
27.         }  
28.         else  
29.         {  
30.             d=d+4*x-4*y+10;  
31.             y=y-1;  
32.         }  
33.         x=x+1;  
34.         eightWaySymmetricPlot(xc,yc,x,y);  
35.     }  
36. }  
37. int main(void)  
38. {  
39.     int gdriver = DETECT, gmode, errorcode;  
40.     int xc,yc,r;  
41.     initgraph(&gdriver, &gmode, "c:\\turboc3\\bgi");  
42. errorcode = graphresult();  
43. if (errorcode != grOk)    
44.     {  
45.         printf("Graphics error: %s\n", grapherrormsg(errorcode));  
46.         printf("Press any key to halt:");  
47.         getch();  
48.         exit(1);               
49.     }  
50. printf("Enter the values of xc and yc ,that is center points of circle : ");  
51.     scanf("%d%d",&xc,&yc);  
52.     printf("Enter the radius of circle : ");  
53.     scanf("%d",&r);  
54.     PolarCircle(xc,yc,r);  
55.     getch();  
56.     closegraph();  
57.     return 0;  
58. }  

Output: