/* calculate cos(x) with Taylor-Polynom 
 * Apel Roland
 * 16.1.97
 */
#include <stdio.h>
#include <math.h>

#define CALCTYPE float
#define SQR(x) (x*x)
/* stop if effect of next interation is to small */
#define EPSILON 0.000001
#define ABS(x) fabs(x)

CALCTYPE kosinus = 0.;
CALCTYPE term = 1.; 
CALCTYPE k2 = 0; 

CALCTYPE cosinus(CALCTYPE x)
{
  while (ABS(term) > ABS(kosinus)*EPSILON)
  {
    kosinus = kosinus + term;
    k2 = k2 + 2;
    term = (-term*SQR(x))/ (CALCTYPE) (k2*(k2-1));
  }
  return(kosinus);
}

int main (int argc, char ** argv)
{
 if (argc != 2)
 {
   fprintf(stderr, "usage: %s <angle in rad> \n" \
                   "       e.g. %s 3.1415 \n", argv[0], argv[0]);
   return(1); 

 }
 printf("result: %f \n",cosinus( atof(argv[1]) ) );
 return (0);
}