1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
2 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
3 .\" <mtk.manpages@gmail.com>
5 .\" %%%LICENSE_START(VERBATIM)
6 .\" Permission is granted to make and distribute verbatim copies of this
7 .\" manual provided the copyright notice and this permission notice are
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10 .\" Permission is granted to copy and distribute modified versions of this
11 .\" manual under the conditions for verbatim copying, provided that the
12 .\" entire resulting derived work is distributed under the terms of a
13 .\" permission notice identical to this one.
15 .\" Since the Linux kernel and libraries are constantly changing, this
16 .\" manual page may be incorrect or out-of-date. The author(s) assume no
17 .\" responsibility for errors or omissions, or for damages resulting from
18 .\" the use of the information contained herein. The author(s) may not
19 .\" have taken the same level of care in the production of this manual,
20 .\" which is licensed free of charge, as they might when working
23 .\" Formatted or processed versions of this manual, if unaccompanied by
24 .\" the source, must acknowledge the copyright and authors of this work.
27 .\" References consulted:
28 .\" Linux libc source code
29 .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
31 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
32 .\" Modified 2002-07-27 by Walter Harms
33 .\" (walter.harms@informatik.uni-oldenburg.de)
35 .TH ATAN2 3 2010-09-20 "" "Linux Programmer's Manual"
37 atan2, atan2f, atan2l \- arc tangent function of two variables
42 .BI "double atan2(double " y ", double " x );
43 .BI "float atan2f(float " y ", float " x );
44 .BI "long double atan2l(long double " y ", long double " x );
50 Feature Test Macro Requirements for glibc (see
51 .BR feature_test_macros (7)):
58 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
59 _POSIX_C_SOURCE\ >=\ 200112L;
68 function calculates the principal value of the arc tangent of
70 using the signs of the two arguments to determine
71 the quadrant of the result.
73 On success, these functions return the principal value of the arc tangent of
75 in radians; the return value is in the range [\-pi,\ pi].
81 is less than 0, +pi (\-pi) is returned.
87 is greater than 0, +0 (\-0) is returned.
93 is +0 or \-0, \-pi/2 is returned.
99 is +0 or \-0, pi/2 is returned.
104 .\" is 0, a pole error shall not occur.
110 is NaN, a NaN is returned.
113 .\" If the result underflows, a range error may occur and
115 .\" should be returned.
121 is \-0, +pi (\-pi) is returned.
127 is +0, +0 (\-0) is returned.
131 is a finite value greater (less) than 0, and
133 is negative infinity, +pi (\-pi) is returned.
137 is a finite value greater (less) than 0, and
139 is positive infinity, +0 (\-0) is returned.
143 is positive infinity (negative infinity), and
146 pi/2 (\-pi/2) is returned.
150 is positive infinity (negative infinity) and
152 is negative infinity, +3*pi/4 (\-3*pi/4) is returned.
156 is positive infinity (negative infinity) and
158 is positive infinity, +pi/4 (\-pi/4) is returned.
161 .\" If both arguments are 0, a domain error shall not occur.
164 .\" POSIX.1 documents an optional underflow error
165 .\" glibc 2.8 does not do this.
168 The variant returning