Subversion Repositories planix.SVN

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

        The exponential function is called for arguments
        greater in magnitude than 0.5.

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

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

#include <math.h>
#include <errno.h>

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;

double
sinh(double arg)
{
        double temp, argsq;
        int sign;

        sign = 1;
        if(arg < 0) {
                arg = - arg;
                sign = -1;
        }
        if(arg > 21) {
                if(arg >= HUGE_VAL){
                        errno = ERANGE;
                        temp = HUGE_VAL;
                } else
                        temp = exp(arg)/2;
                if(sign > 0)
                        return temp;
                else
                        return -temp;
        }

        if(arg > 0.5)
                return sign*(exp(arg) - exp(-arg))/2;

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

double
cosh(double arg)
{
        if(arg < 0)
                arg = - arg;
        if(arg > 21) {
                if(arg >= HUGE_VAL){
                        errno = ERANGE;
                        return HUGE_VAL;
                } else
                        return(exp(arg)/2);
        }
        return (exp(arg) + exp(-arg))/2;
}