1 /*	$OpenBSD: s_cacosl.c,v 1.3 2011/07/20 21:02:51 martynas Exp $	*/
2 
3 /*
4  * Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net>
5  *
6  * Permission to use, copy, modify, and distribute this software for any
7  * purpose with or without fee is hereby granted, provided that the above
8  * copyright notice and this permission notice appear in all copies.
9  *
10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17  */
18 
19 /*							cacosl()
20  *
21  *	Complex circular arc cosine
22  *
23  *
24  *
25  * SYNOPSIS:
26  *
27  * long double complex cacosl();
28  * long double complex z, w;
29  *
30  * w = cacosl( z );
31  *
32  *
33  *
34  * DESCRIPTION:
35  *
36  *
37  * w = arccos z  =  PI/2 - arcsin z.
38  *
39  *
40  *
41  *
42  * ACCURACY:
43  *
44  *                      Relative error:
45  * arithmetic   domain     # trials      peak         rms
46  *    DEC       -10,+10      5200      1.6e-15      2.8e-16
47  *    IEEE      -10,+10     30000      1.8e-14      2.2e-15
48  */
49 
50 #include <complex.h>
51 #include <math.h>
52 
53 static const long double PIO2L = 1.570796326794896619231321691639751442098585L;
54 
55 long double complex
56 cacosl(long double complex z)
57 {
58 	long double complex w;
59 
60 	w = casinl(z);
61 	w = (PIO2L - creall(w)) - cimagl(w) * I;
62 	return (w);
63 }
64