/* tan.c - math routines *//* Copyright 1992-1993 Wind River Systems, Inc. *//*modification history--------------------01f,05feb93,jdi  doc changes based on kdl review.01e,02dec92,jdi  doc tweaks.01d,28oct92,jdi  documentation cleanup.01c,21sep92,smb  changed function header for mg.01b,20sep92,smb  documentation additions01a,08jul92,smb  documentation.*//*DESCRIPTION* Copyright (c) 1987 Regents of the University of California.* All rights reserved.** Redistribution and use in source and binary forms are permitted* provided that the above copyright notice and this paragraph are* duplicated in all such forms and that any documentation,* advertising materials, and other materials related to such* distribution and use acknowledge that the software was developed* by the University of California, Berkeley.  The name of the* University may not be used to endorse or promote products derived* from this software without specific prior written permission.* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.** All recipients should regard themselves as participants in an ongoing* research project and hence should feel obligated to report their* experiences (good or bad) with these elementary function codes, using* the sendbug(8) program, to the authors.*SEE ALSO: American National Standard X3.159-1989NOMANUAL*/#include "vxWorks.h"#include "math.h"#include "private/trigP.h"/********************************************************************************* tan - compute a tangent (ANSI)** This routine computes the tangent of <x> in double precision.* The angle <x> is expressed in radians.* * INCLUDE FILES: math.h** RETURNS: The double-precision tangent of <x>.** SEE ALSO: mathALib*/double tan    (    double x	/* angle in radians */    )    {	double a,z,ss,cc,c;	int k;	if(!finite(x))		/* tan(NaN) and tan(INF) must be NaN */		return x-x;	x = drem(x,PI);			/* reduce x into [-PI/2, PI/2] */	a = copysign(x,one);		/* ... = abs(x) */	if (a >= PIo4) {		k = 1;		x = copysign(PIo2-a,x);	}	else {		k = 0;		if (a < small) {			big+a;			return x;		}	}	z = x*x;	cc = cos__C(z);	ss = sin__S(z);	z *= half;			/* Next get c = cos(x) accurately */	c = (z >= thresh ? half-((z-half)-cc) : one-(z-cc));	if (k == 0)		return x+(x*(z-(cc-ss)))/c;	/* ... sin/cos */#ifdef national	else if (x == zero)		return copysign(fmax,x);	/* no inf on 32k */#endif	/* national */	else		return c/(x+x*ss);		/* ... cos/sin */    }