/* void	_CosDecSmall(pDst,pSrc)
 *
 * ARGUMENT
 *	DEC	*pDst, *pSrc;
 *
 * DESCRIPTION
 *	Sets pDst = cos(pSrc), where 0 <= pSrc < pi / 4.
 *
 * SIDE	EFFECTS
 *	None.
 *
 * RETURNS
 *	None.
 *
 * ALGORITHM
 *  Using the Taylor series,
 *	cos(x) = 1 - x^2/2! + x^4/4! - ...
 *
 * AUTHOR
 *  Jared Levy		April 7, 1987
 *   Copyright (C) 1987-1990 Greenleaf Software	Inc.  All rights reserved.
 *
 * MODIFICATIONS
 *
 */

#include <stdio.h>
#include "gm.h"
#include "gmsystem.h"

void	_CosDecSmall(pDst,pSrc)
DEC	*pDst, *pSrc;
{
	DEC	*srcsq,	dsrcsq,	*term, dterm, *fact, dfact;
	SHORT	i;

	srcsq =	&dsrcsq;
	(void) _MulDec80Bit(srcsq, pSrc, pSrc);
	(void) ConvLongToDecimal(pDst, 1L);
	term = &dterm;
	(void) _MulDec80Bit(term, srcsq, &decPoint5);
	i = 2;
	fact = ConvLongToDecimal(&dfact, 6L);
	while (!(_MacIsDecZ(term)))  {
		if ((i % 4) == 0)
			(void) _AddDec80Bit(pDst, pDst,	term);
		else
			(void) _SubDec80Bit(pDst, pDst,	term);
		i+=2;
		_MulDec80Bit(term, term, srcsq);
		fact->dc.sl[0] = i * (i	- 1);
		_DivRndDec80Bit(term, term, fact, 23);
		}

}