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1 | .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) |
2 | .\" | |
3 | .\" Permission is granted to make and distribute verbatim copies of this | |
4 | .\" manual provided the copyright notice and this permission notice are | |
5 | .\" preserved on all copies. | |
6 | .\" | |
7 | .\" Permission is granted to copy and distribute modified versions of this | |
8 | .\" manual under the conditions for verbatim copying, provided that the | |
9 | .\" entire resulting derived work is distributed under the terms of a | |
10 | .\" permission notice identical to this one. | |
11 | .\" | |
12 | .\" Since the Linux kernel and libraries are constantly changing, this | |
13 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
14 | .\" responsibility for errors or omissions, or for damages resulting from | |
15 | .\" the use of the information contained herein. The author(s) may not | |
16 | .\" have taken the same level of care in the production of this manual, | |
17 | .\" which is licensed free of charge, as they might when working | |
18 | .\" professionally. | |
19 | .\" | |
20 | .\" Formatted or processed versions of this manual, if unaccompanied by | |
21 | .\" the source, must acknowledge the copyright and authors of this work. | |
22 | .\" | |
23 | .\" References consulted: | |
24 | .\" Linux libc source code | |
25 | .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) | |
26 | .\" 386BSD man pages | |
27 | .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu) | |
28 | .\" Modified 2002-07-27 by Walter Harms | |
29 | .\" (walter.harms@informatik.uni-oldenburg.de) | |
30 | .\" | |
31 | .TH ATAN2 3 2002-07-27 "" "Linux Programmer's Manual" | |
32 | .SH NAME | |
33 | atan2, atan2f, atan2l \- arc tangent function of two variables | |
34 | .SH SYNOPSIS | |
35 | .nf | |
36 | .B #include <math.h> | |
37 | .sp | |
38 | .BI "double atan2(double " y ", double " x ); | |
39 | .sp | |
40 | .BI "float atan2f(float " y ", float " x ); | |
41 | .sp | |
42 | .BI "long double atan2l(long double " y ", long double " x ); | |
43 | .sp | |
44 | .fi | |
45 | Link with \-lm. | |
46 | .SH DESCRIPTION | |
47 | The \fBatan2()\fP function calculates the arc tangent of the two | |
48 | variables \fIx\fP and \fIy\fP. It is similar to calculating the | |
49 | arc tangent of \fIy\fP / \fIx\fP, except that the signs of both | |
50 | arguments are used to determine the quadrant of the result. | |
51 | .SH "RETURN VALUE" | |
52 | The \fBatan2()\fP function returns the result in radians, which | |
53 | is between -PI and PI (inclusive). | |
54 | .SH "CONFORMING TO" | |
55 | SVID 3, POSIX, BSD 4.3, ISO 9899. | |
56 | The float and long double variants are C99 requirements. | |
57 | .SH "SEE ALSO" | |
58 | .BR acos (3), | |
59 | .BR asin (3), | |
60 | .BR atan (3), | |
61 | .BR cos (3), | |
62 | .BR sin (3), | |
63 | .BR tan (3) |