#include "stdio.h"
#include "math.h"
main()
{ FILE *fp;
  float y;
  float dt=3.1415926/8,t;
  int i,np;
  printf("Please input sample numbers\n");
  scanf("%d",&np);
  printf("np=%d\n",np);
  fp=fopen("y.xls","w");
  for(i=-np/2;i<=np/2;i++)
    { t=i*dt;
     if(t==0.0)y=1.0;
     else y=sin(t)/t;

    fprintf(fp,".5f   \t  .5f \n",t,y);
    }
  fclose(fp);
}