tan()                   Calculate Tangent

 #include   <math.h>

 double     tan(x);                      Tangent
 double     x;                           Radians

    tan() returns the tangent of 'x' radians.

       Returns:     Tangent of 'x'.  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:     Error handling can be modified with the matherr()
                    function.

                    TLOSS first occurs with 'x' greater than 9.0E15.

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

    The following statements print the tangent of 2 pi radians and 4.9e7
    pi radians and check for any loss of significance.

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

           main()
           {
               double tangent, pi = 3.1415926535;

               tangent = tan(2.0 * pi);
               printf("tangent of 2 * pi = %e\n", tangent);
               errno = 0;
               tangent = tan(4.9e7 * pi);
               /* if a TLOSS error occurs, a message is printed to stderr */
               if (errno == ERANGE)
                   printf("ERANGE error in tan()\n");
               printf("tangent of 4.9e7 * pi = %e\n", tangent);
           }