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cos()                    Calculate Cosine

 #include <math.h>

 double     cos(x);                      Cosine
 double     x;                           Radians

    cos() returns the cosine of 'x' radians.

    Returns:    Cosine of 'x'.  If 'x' is large, a partial loss of
                significance in the result may occur, in which case
                matherr() is called with a PLOSS error, 'errno' (defined
                in <stdlib.h>) is set to ERANGE (defined in <math.h>),
                and the partially insignificant result is returned.  If
                'x' is so large that a total loss of significance occurs,
                then matherr() is called with a TLOSS error, a TLOSS
                error message is printed to 'stderr', 'errno' is set to
                ERANGE, and 0.0 is returned.

      Notes:    PLOSS first occurs at 'x' greater than 1.0E8.
                TLOSS first occurs at 'x' greater than 2.0E9.

                Error handling can be modified by using the matherr()
                function.

  -------------------------------- Example ---------------------------------

    The following statements print the cosine of pi radians and 5.2e8 pi
    radians, and check for any loss of significance.

         #include <math.h>       /* for cos() and ERANGE */
         #include <stdio.h>      /* for printf() */
         #include <stdlib.h>     /* for errno */

         main()
         {
             double cosine, pi = 3.1415926535;

             cosine = cos(pi);
             printf("cosine of pi = %e\n", cosine);
             errno = 0;
             cosine = cos(5.2e8 * pi);
             /*if a TLOSS error occurs, a message is also printed to stderr*/
             if (errno == ERANGE)
                 printf("ERANGE error in cos()\n");
             printf("cosine of 5.2e8 * pi = %e\n", cosine);
         }