Subversion Repositories planix.SVN

/*
        asin(arg) and acos(arg) return the arcsin, arccos,
        respectively of their arguments.

        Arctan is called after appropriate range reduction.
 */

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

static double pio2      = 1.570796326794896619231e0;

double
asin(double arg)
{
        double temp;
        int sign;

        sign = 0;
        if(arg < 0) {
                arg = -arg;
                sign++;
        }
        if(arg > 1) {
                errno = EDOM;
                return 0;
        }
        temp = sqrt(1 - arg*arg);
        if(arg > 0.7)
                temp = pio2 - atan(temp/arg);
        else
                temp = atan(arg/temp);

        if(sign)
                temp = -temp;
        return temp;
}

double
acos(double arg)
{
        if(arg > 1 || arg < -1) {
                errno = EDOM;
                return 0;
        }
        return pio2 - asin(arg);
}