#include <soft.h>

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

	Arctan is called after appropriate range reduction.

	need error handling
*/

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

	sign = 1.;
	if(arg <0.0){
		arg = -arg;
		sign = -1.;
	}

	if(arg > 1.){
		errno = EDOM;
		perror ("asin");
		return(0.);
	}

	temp = sqrt(1. - arg*arg);
	if(arg > 0.7)
		temp = pio2 - atan(temp/arg);
	else
		temp = atan(arg/temp);

	return(sign*temp);
}

double acos(double arg)
{
	if((arg > 1.) || (arg < -1.)){
		errno = EDOM;
		perror ("acos");
		return(0.);
	}

	return(pio2 - asin(arg));
}