/*
 * 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.
 */
#include <math.h>

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));
}
