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/*
* IBM Accurate Mathematical Library
* written by International Business Machines Corp.
* Copyright (C) 2001-2020 Free Software Foundation, Inc.
*
* This program 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 2.1 of the License, or
* (at your option) any later version.
*
* This program 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/>.
*/
/**********************************************************************/
/* MODULE_NAME:mptan.c */
/* */
/* FUNCTION: mptan */
/* */
/* FILES NEEDED: endian.h mpa.h */
/* mpa.c sincos32.c branred.c */
/* */
/* Multi-Precision tan() function subroutine, for p=32. It is based */
/* on the routines mpranred() and c32(). mpranred() performs range */
/* reduction of a double number x into a multiple precision number */
/* y, such that y=x-n*pi/2, abs(y)<pi/4, n=0,+-1,+-2,.... c32() */
/* computes both sin(y), cos(y). tan(x) is either sin(y)/cos(y) */
/* or -cos(y)/sin(y). The precision of the result is of about 559 */
/* significant bits. */
/* */
/**********************************************************************/
#include "endian.h"
#include "mpa.h"
#ifndef SECTION
# define SECTION
#endif
void
SECTION
__mptan (double x, mp_no *mpy, int p)
{
int n;
mp_no mpw, mpc, mps;
/* Negative or positive result. */
n = __mpranred (x, &mpw, p) & 0x00000001;
/* Computing sin(x) and cos(x). */
__c32 (&mpw, &mpc, &mps, p);
/* Second or fourth quarter of unit circle. */
if (n)
{
__dvd (&mpc, &mps, mpy, p);
mpy->d[0] *= -1;
}
/* tan is negative in this area. */
else
__dvd (&mps, &mpc, mpy, p);
}
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