forked from KolibriOS/kolibrios
115 lines
2.4 KiB
C
115 lines
2.4 KiB
C
|
|
/* @(#)s_tan.c 5.1 93/09/24 */
|
|
/*
|
|
* ====================================================
|
|
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
|
|
*
|
|
* Developed at SunPro, a Sun Microsystems, Inc. business.
|
|
* Permission to use, copy, modify, and distribute this
|
|
* software is freely granted, provided that this notice
|
|
* is preserved.
|
|
* ====================================================
|
|
*/
|
|
|
|
|
|
/*
|
|
|
|
FUNCTION
|
|
<<tan>>, <<tanf>>---tangent
|
|
|
|
INDEX
|
|
tan
|
|
INDEX
|
|
tanf
|
|
|
|
ANSI_SYNOPSIS
|
|
#include <math.h>
|
|
double tan(double <[x]>);
|
|
float tanf(float <[x]>);
|
|
|
|
TRAD_SYNOPSIS
|
|
#include <math.h>
|
|
double tan(<[x]>)
|
|
double <[x]>;
|
|
|
|
float tanf(<[x]>)
|
|
float <[x]>;
|
|
|
|
|
|
DESCRIPTION
|
|
<<tan>> computes the tangent of the argument <[x]>.
|
|
Angles are specified in radians.
|
|
|
|
<<tanf>> is identical, save that it takes and returns <<float>> values.
|
|
|
|
RETURNS
|
|
The tangent of <[x]> is returned.
|
|
|
|
PORTABILITY
|
|
<<tan>> is ANSI. <<tanf>> is an extension.
|
|
*/
|
|
|
|
/* tan(x)
|
|
* Return tangent function of x.
|
|
*
|
|
* kernel function:
|
|
* __kernel_tan ... tangent function on [-pi/4,pi/4]
|
|
* __ieee754_rem_pio2 ... argument reduction routine
|
|
*
|
|
* Method.
|
|
* Let S,C and T denote the sin, cos and tan respectively on
|
|
* [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
|
|
* in [-pi/4 , +pi/4], and let n = k mod 4.
|
|
* We have
|
|
*
|
|
* n sin(x) cos(x) tan(x)
|
|
* ----------------------------------------------------------
|
|
* 0 S C T
|
|
* 1 C -S -1/T
|
|
* 2 -S -C T
|
|
* 3 -C S -1/T
|
|
* ----------------------------------------------------------
|
|
*
|
|
* Special cases:
|
|
* Let trig be any of sin, cos, or tan.
|
|
* trig(+-INF) is NaN, with signals;
|
|
* trig(NaN) is that NaN;
|
|
*
|
|
* Accuracy:
|
|
* TRIG(x) returns trig(x) nearly rounded
|
|
*/
|
|
|
|
#include "fdlibm.h"
|
|
|
|
#ifndef _DOUBLE_IS_32BITS
|
|
|
|
#ifdef __STDC__
|
|
double tan(double x)
|
|
#else
|
|
double tan(x)
|
|
double x;
|
|
#endif
|
|
{
|
|
double y[2],z=0.0;
|
|
__int32_t n,ix;
|
|
|
|
/* High word of x. */
|
|
GET_HIGH_WORD(ix,x);
|
|
|
|
/* |x| ~< pi/4 */
|
|
ix &= 0x7fffffff;
|
|
if(ix <= 0x3fe921fb) return __kernel_tan(x,z,1);
|
|
|
|
/* tan(Inf or NaN) is NaN */
|
|
else if (ix>=0x7ff00000) return x-x; /* NaN */
|
|
|
|
/* argument reduction needed */
|
|
else {
|
|
n = __ieee754_rem_pio2(x,y);
|
|
return __kernel_tan(y[0],y[1],1-((n&1)<<1)); /* 1 -- n even
|
|
-1 -- n odd */
|
|
}
|
|
}
|
|
|
|
#endif /* _DOUBLE_IS_32BITS */
|