dsin.c

来自「speech signal process tools」· C语言 代码 · 共 42 行

#include "defcons.h"
/* sin routine */
double dsin(x)
register double x;
{
	register double sum,term,xsq;
	register int i;

	sum=two_pi;
	if(x<0)
		{
		x/= -sum;
		x-=(int)x;
		x*=sum;
		xsq=(-x*x);
		term=sum=x;
		x=1e-18;
		for(i=2;((term<0)?-term:term)>x;i+=2)
			{
			term*=xsq/(i*(i+1));
			sum+=term;
			}
		sum=sum>1?1:sum;
		sum=sum<-1?-1:sum;
		return(-sum);
		}
	x/=sum;
	x-=(int)x;
	x*=sum;
	xsq=(-x*x);
	term=sum=x;
	x=1e-16;
	for(i=2;((term<0)?-term:term)>x;i+=2)
		{
		term*=xsq/(i*(i+1));
		sum+=term;
		}
	sum=sum>1?1:sum;
	sum=sum<-1?-1:sum;
	return(sum);
}