tanh()                  Calculate Hyperbolic Tangent

 #include   <math.h>

 double     tanh(x);
 double     x;                           Radians

    tanh() returns the hyperbolic tangent of 'x'.

       Returns:     The hyperbolic tangent of 'x'.  There is no error
                    return.

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

    The following statements print the hyperbolic tangent of -3.1416.

           #include <math.h>
           #include <stdio.h>       /* for printf() */

           main()
           {
               double htangent;

               htangent = tanh(-3.1416);  /* htangent = -0.9962721 */
               printf("hyperbolic tangent of -3.1416 radians = %e\n",
                       htangent);
           }