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[glibc/history.git] / math / s_ctan.c
blob0464ab86d598bfc720c99d0fbd607a4f10606af7
1 /* Complex tangent function for double.
2 Copyright (C) 1997, 2005 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, write to the Free
18 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
19 02111-1307 USA. */
21 #include <complex.h>
22 #include <fenv.h>
23 #include <math.h>
25 #include "math_private.h"
28 __complex__ double
29 __ctan (__complex__ double x)
31 __complex__ double res;
33 if (!isfinite (__real__ x) || !isfinite (__imag__ x))
35 if (__isinf (__imag__ x))
37 __real__ res = __copysign (0.0, __real__ x);
38 __imag__ res = __copysign (1.0, __imag__ x);
40 else if (__real__ x == 0.0)
42 res = x;
44 else
46 __real__ res = __nan ("");
47 __imag__ res = __nan ("");
49 #ifdef FE_INVALID
50 if (__isinf (__real__ x))
51 feraiseexcept (FE_INVALID);
52 #endif
55 else
57 double sin2rx, cos2rx;
58 double den;
60 __sincos (2.0 * __real__ x, &sin2rx, &cos2rx);
62 den = cos2rx + __ieee754_cosh (2.0 * __imag__ x);
64 if (den == 0.0)
66 __complex__ double ez = __cexp (1.0i * x);
67 __complex__ double emz = __cexp (-1.0i * x);
69 res = (ez - emz) / (ez + emz) * -1.0i;
71 else
73 __real__ res = sin2rx / den;
74 __imag__ res = __ieee754_sinh (2.0 * __imag__ x) / den;
78 return res;
80 weak_alias (__ctan, ctan)
81 #ifdef NO_LONG_DOUBLE
82 strong_alias (__ctan, __ctanl)
83 weak_alias (__ctan, ctanl)
84 #endif