#include <stdlib.h>
#include <math.h>
#include <conio.h>
#include <graphics.h>
void main()
{
  struct point { int x,y; } p1, pbe;
  int lon,sho,Drive, Mode;
  float i, tx, ty, x, y, min, max;
  int j, wl, x1=0, y1=0, m;

  printf("give me the original point --> "); scanf("%d %d",&p1.x,&p1.y);
  printf("input the range min max --> "); scanf("%f %f",&min,&max);
  printf("give me the wave length --> "); scanf("%d",&wl);
  Drive=DETECT; initgraph(&Drive, &Mode, ""); setcolor(14);
  line(p1.x,0, p1.x,479); line(0,p1.y,639,p1.y); /* coordinate line */
  for (j=m=0,i=min; i<=max; i+=0.05) {

    x=p1.x+i*wl; y=p1.y+wl*tan(i);

    if ((x >= 0) && (x <= 639) && (y >= 0) && (y <= 479)) {
      /* if (j == 0) { moveto(x1,y1); j=1; }
      else lineto(x1,y1); */
      putpixel(x,y,14);
      x1=x; y1=y;  delay(20);
    }
  }
  getche(); closegraph();
}