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/************************************************************************
* lib/math/lib_sin.c
*
* This file is a part of NuttX:
*
* Copyright (C) 2012 Gregory Nutt. All rights reserved.
* Ported by: Darcy Gong
*
* It derives from the Rhombs OS math library by Nick Johnson which has
* a compatibile, MIT-style license:
*
* Copyright (C) 2009-2011 Nick Johnson <nickbjohnson4224 at gmail.com>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
************************************************************************/
/************************************************************************
* Included Files
************************************************************************/
#include <nuttx/config.h>
#include <nuttx/compiler.h>
#include <math.h>
#include <float.h>
/************************************************************************
* Public Functions
************************************************************************/
#ifdef CONFIG_HAVE_DOUBLE
double asin(double x)
{
long double y, y_sin, y_cos;
y = 0;
while (1)
{
y_sin = sin(y);
y_cos = cos(y);
if (y > M_PI_2 || y < -M_PI_2)
{
y = fmod(y, M_PI);
}
if (y_sin + DBL_EPSILON >= x && y_sin - DBL_EPSILON <= x)
{
break;
}
y = y - (y_sin - x) / y_cos;
}
return y;
}
#endif
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