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/* cos (cosine) function with 'long double' argument.
Copyright (C) 2003-2021 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 3 of the
License, or (at your option) any later version.
This file is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* s_cosl.c -- long double version of s_sin.c.
* Conversion to long double by Jakub Jelinek, jj@ultra.linux.cz.
*/
/*
* ====================================================
* 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.
* ====================================================
*/
#include <config.h>
/* Specification. */
#include <math.h>
#if HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
long double
cosl (long double x)
{
return cos (x);
}
#else
/* Code based on glibc/sysdeps/ieee754/ldbl-128/s_cosl.c. */
/* cosl(x)
* Return cosine function of x.
*
* kernel function:
* __kernel_sinl ... sine function on [-pi/4,pi/4]
* __kernel_cosl ... cosine function on [-pi/4,pi/4]
* __ieee754_rem_pio2l ... 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 "trigl.h"
long double
cosl (long double x)
{
long double y[2],z=0.0L;
int n;
/* cosl(NaN) is NaN */
if (isnanl (x))
return x;
/* |x| ~< pi/4 */
if (x >= -0.7853981633974483096156608458198757210492
&& x <= 0.7853981633974483096156608458198757210492)
return kernel_cosl(x, z);
/* cosl(Inf) is NaN, cosl(0) is 1 */
else if (x + x == x && x != 0.0)
return x - x; /* NaN */
/* argument reduction needed */
else
{
n = ieee754_rem_pio2l (x, y);
switch (n & 3)
{
case 0:
return kernel_cosl (y[0], y[1]);
case 1:
return -kernel_sinl (y[0], y[1], 1);
case 2:
return -kernel_cosl (y[0], y[1]);
default:
return kernel_sinl (y[0], y[1], 1);
}
}
}
#endif
#if 0
int
main (void)
{
printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492));
printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *29));
printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *2));
printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *30));
printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *4));
printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *32));
printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *2/3));
printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *4/3));
}
#endif
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