Bell 32V development

[unix-history] / usr / src / libF77 / tanh.c

/*
       tanh(arg) computes the hyperbolic tangent of its floating
       point argument.

       sinh and cosh are called except for large arguments, which
       would cause overflow improperly.
*/

double sinh(), cosh();

double
tanh(arg) double arg; {

       double sign;

       sign = 1.;
       if(arg < 0.){
               arg = -arg;
               sign = -1.;
       }

       if(arg > 21.){
               return(sign);
       }

       return(sign*sinh(arg)/cosh(arg));
}