/***************************************************************************
 *                               RasMol 2.7.3                              *
 *                                                                         *
 *                                 RasMol                                  *
 *                 Molecular Graphics Visualisation Tool                   *
 *                             6 February 2005                             *
 *                                                                         *
 *                   Based on RasMol 2.6 by Roger Sayle                    *
 * Biomolecular Structures Group, Glaxo Wellcome Research & Development,   *
 *                      Stevenage, Hertfordshire, UK                       *
 *         Version 2.6, August 1995, Version 2.6.4, December 1998          *
 *                   Copyright (C) Roger Sayle 1992-1999                   *
 *                                                                         *
 *                          and Based on Mods by                           *
 *Author             Version, Date             Copyright                   *
 *Arne Mueller       RasMol 2.6x1   May 98     (C) Arne Mueller 1998       *
 *Gary Grossman and  RasMol 2.5-ucb Nov 95     (C) UC Regents/ModularCHEM  *
 *Marco Molinaro     RasMol 2.6-ucb Nov 96         Consortium 1995, 1996   *
 *                                                                         *
 *Philippe Valadon   RasTop 1.3     Aug 00     (C) Philippe Valadon 2000   *
 *                                                                         *
 *Herbert J.         RasMol 2.7.0   Mar 99     (C) Herbert J. Bernstein    * 
 *Bernstein          RasMol 2.7.1   Jun 99         1998-2001               *
 *                   RasMol 2.7.1.1 Jan 01                                 *
 *                   RasMol 2.7.2   Aug 00                                 *
 *                   RasMol 2.7.2.1 Apr 01                                 *
 *                   RasMol 2.7.2.1.1 Jan 04                               *
 *                   RasMol 2.7.3   Feb 05                                 *
 *                                                                         *
 *with RasMol 2.7.3 incorporating changes by Clarice Chigbo, Ricky Chachra,*
 *and Mamoru Yamanishi.  Work on RasMol 2.7.3 supported in part by         *
 *grants DBI-0203064, DBI-0315281 and EF-0312612 from the U.S. National    *
 *Science Foundation and grant DE-FG02-03ER63601 from the U.S. Department  *
 *of Energy.                                                               *
 *                                                                         *
 *                    and Incorporating Translations by                    *
 *  Author                               Item                      Language*
 *  Isabel Servan Martinez,                                                *
 *  Jose Miguel Fernandez Fernandez      2.6   Manual              Spanish *
 *  Jose Miguel Fernandez Fernandez      2.7.1 Manual              Spanish *
 *  Fernando Gabriel Ranea               2.7.1 menus and messages  Spanish *
 *  Jean-Pierre Demailly                 2.7.1 menus and messages  French  *
 *  Giuseppe Martini, Giovanni Paolella, 2.7.1 menus and messages          *
 *  A. Davassi, M. Masullo, C. Liotto    2.7.1 help file           Italian *
 *                                                                         *
 *                             This Release by                             *
 * Herbert J. Bernstein, Bernstein + Sons, P.O. Box 177, Bellport, NY, USA *
 *                       yaya@bernstein-plus-sons.com                      *
 *               Copyright(C) Herbert J. Bernstein 1998-2005               *
 *                                                                         *
 *                READ THE FILE NOTICE FOR RASMOL LICENSES                 *
 *Please read the file NOTICE for important notices which apply to this    *
 *package and for license terms (GPL or RASLIC).                           *
 ***************************************************************************/
/* acos.c
 * Herbert J. Bernstein, September 1999
 * yaya@bernstein-plus-sons.com
 *
 * Replacement math.h acos, using atan2 for an acos which is
 * erroneous in some libraries
 * 
 * Rev 21 February 1999
 */


#include <math.h>

double acos(double x)
{
	
	register double y;
	
	y = sqrt(1.-x*x);
	
	return atan2(y,x);
}