char
float_arccos(
floatnum x,
int digits)
{
if (!chckmathparam(x, digits))
return 0;
if (float_abscmp(x, &c1) > 0)
return _seterror(x, OutOfDomain);
_arccos(x, digits);
return 1;
}
/* evaluates arccos (1+x) for -2 <= x <= 0.
The result is in the range 0 <= x <= pi */
void
_arccosxplus1(
floatnum x,
int digits)
{
if (float_abscmp(x, &c1Div2) <= 0)
_arccosxplus1lt0_5(x, digits);
else
{
float_add(x, x, &c1, digits);
_arccos(x, digits);
}
}
/* evaluates arcsin x for -1 <= x <= 1.
The result is in the range -pi/2 <= result <= pi/2
The relative error for a 100 digit result is < 8e-100 */
void
_arcsin(
floatnum x,
int digits)
{
signed char sgn;
if (float_abscmp(x, &c1Div2) <= 0)
_arcsinlt0_5(x, digits);
else
{
sgn = float_getsign(x);
float_abs(x);
_arccos(x, digits);
float_sub(x, &cPiDiv2, x, digits);
float_setsign(x, sgn);
}
}
