/*
    Copyright (C) 2015 Fredrik Johansson

    This file is part of Arb.

    Arb is free software: you can redistribute it and/or modify it under
    the terms of the GNU Lesser General Public License (LGPL) as published
    by the Free Software Foundation; either version 2.1 of the License, or
    (at your option) any later version.  See <http://www.gnu.org/licenses/>.
*/

#include "acb.h"

void
acb_acos(acb_t res, const acb_t z, slong prec)
{
    if (acb_is_one(z))
    {
        acb_zero(res);
    }
    else
    {
        acb_t t;
        acb_init(t);
        acb_asin(res, z, prec);
        acb_const_pi(t, prec);
        acb_mul_2exp_si(t, t, -1);
        acb_sub(res, t, res, prec);
        acb_clear(t);
    }
}