ref: 8188b4f4f0e07b6669e6ae3c6c1099af917eaab4
dir: /sys/src/libc/port/sinh.c/
#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;
}