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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#pragma ident "@(#)cosl.c 1.9 06/01/31 SMI"
#pragma weak cosl = __cosl
/* INDENT OFF */
/* cosl(x)
* Table look-up algorithm by K.C. Ng, November, 1989.
*
* kernel function:
* __k_sinl ... sin function on [-pi/4,pi/4]
* __k_cosl ... cos function on [-pi/4,pi/4]
* __rem_pio2l ... argument reduction routine
*
* Method.
* Let S and C denote the sin and cos respectively on [-PI/4, +PI/4].
* 1. Assume the argument x is reduced to y1+y2 = x-k*pi/2 in
* [-pi/2 , +pi/2], and let n = k mod 4.
* 2. Let S=S(y1+y2), C=C(y1+y2). Depending on n, we have
*
* n sin(x) cos(x) tan(x)
* ----------------------------------------------------------
* 0 S C S/C
* 1 C -S -C/S
* 2 -S -C S/C
* 3 -C S -C/S
* ----------------------------------------------------------
*
* Special cases:
* Let trig be any of sin, cos, or tan.
* trig(+-INF) is NaN, with signals;
* trig(NaN) is that NaN;
*
* Accuracy:
* computer TRIG(x) returns trig(x) nearly rounded.
*/
/* INDENT ON */
#include "libm.h"
#include "libm_synonyms.h"
#include "longdouble.h"
long double
cosl(long double x) {
long double y[2], z = 0.0L;
int n, ix;
int *px = (int *) &x;
/* trig(Inf or NaN) is NaN */
if (!finitel(x))
return x - x;
/* High word of x. */
#if !defined(__i386)
ix = px[0];
#else
XTOI(px, ix);
#endif
/* |x| ~< pi/4 */
ix &= 0x7fffffff;
if (ix <= 0x3ffe9220)
return __k_cosl(x, z);
/* argument reduction needed */
else {
n = __rem_pio2l(x, y);
switch (n & 3) {
case 0:
return __k_cosl(y[0], y[1]);
case 1:
return -__k_sinl(y[0], y[1]);
case 2:
return -__k_cosl(y[0], y[1]);
case 3:
return __k_sinl(y[0], y[1]);
/* NOTREACHED */
}
}
}
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