3BSD/usr/src/libF77/sinh.c

/*
	sinh(arg) returns the hyperbolic sign of its floating-
	point argument.

	The exponential function is called for arguments
	greater in magnitude than 0.5.
	The result overflows and 'huge' is returned for
	arguments greater than somewhat.

	A series is used for arguments smaller in magnitude than 0.5.
	The coeffieients are #2029 from Hart & Cheney. (20.36D)

	cosh(arg) is computed from the exponential function for
	all arguments.
*/

double exp();

static double p0 -0.6307673640497716991184787251e+6;
static double p1 -0.8991272022039509355398013511e+5;
static double p2 -0.2894211355989563807284660366e+4;
static double p3 -0.2630563213397497062819489e+2;
static double q0 -0.6307673640497716991212077277e+6;
static double q1  0.1521517378790019070696485176e+5;
static double q2 -0.173678953558233699533450911e+3;
static double q3  1.0;

double
sinh(arg) double arg; {

	double sign, temp, argsq;

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

	if(arg > 21.){
		temp = exp(arg)/2;
		return(sign*temp);
	}

	if(arg > 0.5) {
		temp = (exp(arg) - exp(-arg))/2;
		return(sign*temp);
	}

	argsq = arg*arg;
	temp = (((p3*argsq+p2)*argsq+p1)*argsq+p0)*arg;
	temp = temp/(((q3*argsq+q2)*argsq+q1)*argsq+q0);
	return(sign*temp);

}

double
cosh(arg) double arg; {

	double temp;

	if(arg < 0)
		arg = - arg;

	if(arg > 21.){
		temp = exp(arg)/2;
		return(temp);
	}

	temp = (exp(arg) + exp(-arg))/2;
	return(temp);
}