Good Example Of Math in Programming

#include<graphics.h>
#include<math.h>
#include<conio.h>
#define MAXPTS 15
#define PI 3.14159 /* Define a value for PI */

struct PTS {    /* used to get x and y co-ordinates */
int x, y;
};

int main()
{
    struct viewporttype vp;
    struct PTS points[MAXPTS];
    int i, j, h, w, xcenter, ycenter,gd=DETECT,gm;
    int radius, angle, step;
    double rads,AspectRatio;
    int xasp, yasp;     /* Used to read the aspect ratio*/
    initgraph(&gd,&gm,"c:\\tc\\bgi");
    getaspectratio(&xasp,&yasp);
    AspectRatio = (double)xasp / (double)yasp;  /* Get correction factor */
    getviewsettings( &vp );
    h = vp.bottom - vp.top;
    w = vp.right - vp.left;
    xcenter = w / 2;    /* Determine the center of circle */
    ycenter = h / 2;
    radius = (h - 30) / (AspectRatio * 2);
    step = 360 / MAXPTS;    /* Determine # of increments */

    angle = 0;  /* Begin at zero degrees */
    for( i=0 ; i<MAXPTS ; ++i )
    {                       /* Determine circle intercepts */
        rads = (double)angle * PI / 180.0;      /* Convert angle to radians */
        points[i].x = xcenter + (int)( cos(rads) * radius );
        points[i].y = ycenter - (int)( sin(rads) * radius * AspectRatio );
        angle += step;              /* Move to next increment */
    }

    circle( xcenter, ycenter, radius ); /* Draw bounding circle */

    for( i=0 ; i<MAXPTS ; ++i )
    {                       /* Draw the cords to the circle */
        for( j=i ; j<MAXPTS ; ++j )
        {               /* For each remaining intersect */
            moveto(points[i].x, points[i].y);   /* Move to beginning of cord */
            lineto(points[j].x, points[j].y);   /* Draw the cord */
        }
    }
getch();
}