getsincos.c

来自「speech signal process tools」· C语言 代码 · 共 50 行

#include "defcons.h"
getsincos(x,psin,pcos)/* return sin and cos of x */
register double x,*psin,*pcos;
{
	register double sin,cos,term;
	register int i,sign;

	sign=0;
	if(x<0)
		{
		sign=1;
		x= -x;
		}
	x/=two_pi;
	x-=(int)x;
	x*=two_pi;
	sin=0;
	cos=term=1;
	i=1;
	if(x<1e-8)
		{
		cos=1;
		sin=x;
		term=0;
		}
	while((term<0?-term:term)>1e-18)
		{
		term*= -x/i;
		sin-=term;
		i++;
		term*= -x/i;
		cos-=term;
		i++;
		term*= -x/i;
		sin+=term;
		i++;
		term*= -x/i;
		cos+=term;
		i++;
		}
	sin=sin>1?1:sin;
	sin=sin<-1?-1:sin;
	if(sign)sin= -sin;
	*psin=sin;
	cos=cos>1?1:cos;
	cos=cos<-1?-1:cos;
	*pcos=cos;
	return;
}