minix/lib/math/asin.c
2009-11-09 10:26:00 +00:00

82 lines
1.3 KiB
C

/*
* (c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
* See the copyright notice in the ACK home directory, in the file "Copyright".
*
* Author: Ceriel J.H. Jacobs
*/
/* $Header$ */
#include <math.h>
#include <errno.h>
#include "localmath.h"
static double
asin_acos(double x, int cosfl)
{
int negative = x < 0;
int i;
double g;
static double p[] = {
-0.27368494524164255994e+2,
0.57208227877891731407e+2,
-0.39688862997540877339e+2,
0.10152522233806463645e+2,
-0.69674573447350646411e+0
};
static double q[] = {
-0.16421096714498560795e+3,
0.41714430248260412556e+3,
-0.38186303361750149284e+3,
0.15095270841030604719e+3,
-0.23823859153670238830e+2,
1.0
};
if (__IsNan(x)) {
errno = EDOM;
return x;
}
if (negative) {
x = -x;
}
if (x > 0.5) {
i = 1;
if (x > 1) {
errno = EDOM;
return 0;
}
g = 0.5 - 0.5 * x;
x = - sqrt(g);
x += x;
}
else {
/* ??? avoid underflow ??? */
i = 0;
g = x * x;
}
x += x * g * POLYNOM4(g, p) / POLYNOM5(g, q);
if (cosfl) {
if (! negative) x = -x;
}
if ((cosfl == 0) == (i == 1)) {
x = (x + M_PI_4) + M_PI_4;
}
else if (cosfl && negative && i == 1) {
x = (x + M_PI_2) + M_PI_2;
}
if (! cosfl && negative) x = -x;
return x;
}
double
asin(double x)
{
return asin_acos(x, 0);
}
double
acos(double x)
{
return asin_acos(x, 1);
}