/**************************************************************************** * libc/math/lib_sin.c * * This file is a part of NuttX: * * Copyright (C) 2012, 2015 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 * * 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 #include #include #include /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ #undef DBL_EPSILON #define DBL_EPSILON 1e-12 /**************************************************************************** * Public Functions ****************************************************************************/ #ifdef CONFIG_HAVE_DOUBLE double asin(double x) { long double y; long double y_sin; long double y_cos; /* Verify that the input value is in the domain of the function */ if (x < -1.0 || x > 1.0) { return NAN; } 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