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 tan()                   Calculate Tangent

 #include   <math.h>

 double     tan(x);                      Tangent
 double     x;                           Angle in radians

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

    Returns:    Tangent of 'x'.  If 'x' is large, there may be a partial
                loss of significance in the result.  matherr() is then
                called with a PLOSS error, 'errno' (defined in
                <stdlib.h>) is set to ERANGE (defined in <math.h>), and
                the partially significant result is returned.  If 'x' is
                so large there is a total loss of significance, 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.

                PLOSS first occurs with 'x' greater than 1.0E8.

                TLOSS first occurs with 'x' greater than 2.0E9.

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

           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);
           }