#include <stdio.h>
#include <math.h>

int main ()
{
   float a, b, c;      /* Constants of the defining equation */
   float x0, y0, r;    /* Center and radius */
   float x, y;         /* Coordinates of a given point */
   float t;            /* Temporary variable */

   printf("Enter the coefficients of the defining equation :\n");
   printf("a = "); scanf("%f",&a);
   printf("b = "); scanf("%f",&b);
   printf("c = "); scanf("%f",&c);
   t = (a*a+b*b)/4-c;
   if (t < 0) {
      printf("These a,b,c do not define a circle.\n");
   } else {
      x0 = -a/2; y0 = -b/2;
      r = sqrt(t);
      printf("The circle has center at (%f,%f) and radius %f.\n", x0, y0, r);
      printf("Enter the coordinates of a point :\n");
      printf("x = "); scanf("%f",&x);
      printf("y = "); scanf("%f",&y);
      t = sqrt((x-x0)*(x-x0)+(y-y0)*(y-y0));
      if (t == r) printf("The point lies on the circle.\n");
      else if (t < r) printf("The point lies inside the circle.\n");
      else printf("The point lies outside the circle.\n");
   }
}