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

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

        sign = 0;
        if(arg < 0) {
                arg = -arg;
                sign++;
        }
        if(arg > 1)
                return NaN();
        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)
                return NaN();
        return PIO2 - asin(arg);
}