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[unix-history] / usr / src / libm / 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));
}