Subversion Repositories planix.SVN

#include <u.h>
#include <libc.h>

/*
 * 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.
 */

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 = 0;
        if(arg < 0) {
                arg = -arg;
                sign++;
        }
        if(arg > 21) {
                temp = exp(arg)/2;
                goto out;
        }
        if(arg > 0.5) {
                temp = (exp(arg) - exp(-arg))/2;
                goto out;
        }
        argsq = arg*arg;
        temp = (((p3*argsq+p2)*argsq+p1)*argsq+p0)*arg;
        temp /= (((argsq+q2)*argsq+q1)*argsq+q0);
out:
        if(sign)
                temp = -temp;
        return temp;
}

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