1 /*	$OpenBSD: s_cacos.c,v 1.6 2013/07/03 04:46:36 espie Exp $	*/
2 /*
3  * Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net>
4  *
5  * Permission to use, copy, modify, and distribute this software for any
6  * purpose with or without fee is hereby granted, provided that the above
7  * copyright notice and this permission notice appear in all copies.
8  *
9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16  */
17 
18 /*							cacos()
19  *
20  *	Complex circular arc cosine
21  *
22  *
23  *
24  * SYNOPSIS:
25  *
26  * double complex cacos();
27  * double complex z, w;
28  *
29  * w = cacos (z);
30  *
31  *
32  *
33  * DESCRIPTION:
34  *
35  *
36  * w = arccos z  =  PI/2 - arcsin z.
37  *
38  *
39  *
40  *
41  * ACCURACY:
42  *
43  *                      Relative error:
44  * arithmetic   domain     # trials      peak         rms
45  *    DEC       -10,+10      5200      1.6e-15      2.8e-16
46  *    IEEE      -10,+10     30000      1.8e-14      2.2e-15
47  */
48 
49 #include <complex.h>
50 #include <float.h>
51 #include <math.h>
52 
53 double complex
54 cacos(double complex z)
55 {
56 	double complex w;
57 
58 	w = casin (z);
59 	w = (M_PI_2 - creal (w)) - cimag (w) * I;
60 	return (w);
61 }
62 
63 #if	LDBL_MANT_DIG == DBL_MANT_DIG
64 __strong_alias(cacosl, cacos);
65 #endif	/* LDBL_MANT_DIG == DBL_MANT_DIG */
66