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 .\" Permission is granted to make and distribute verbatim copies of this
6 .\" manual provided the copyright notice and this permission notice are
7 .\" preserved on all copies.
9 .\" Permission is granted to copy and distribute modified versions of this
10 .\" manual under the conditions for verbatim copying, provided that the
11 .\" entire resulting derived work is distributed under the terms of a
12 .\" permission notice identical to this one.
14 .\" Since the Linux kernel and libraries are constantly changing, this
15 .\" manual page may be incorrect or out-of-date. The author(s) assume no
16 .\" responsibility for errors or omissions, or for damages resulting from
17 .\" the use of the information contained herein. The author(s) may not
18 .\" have taken the same level of care in the production of this manual,
19 .\" which is licensed free of charge, as they might when working
22 .\" Formatted or processed versions of this manual, if unaccompanied by
23 .\" the source, must acknowledge the copyright and authors of this work.
25 .\" References consulted:
26 .\" Linux libc source code
27 .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
29 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
30 .\" Modified 2002-07-27 by Walter Harms
31 .\" (walter.harms@informatik.uni-oldenburg.de)
33 .TH ATAN2 3 2010-09-20 "" "Linux Programmer's Manual"
35 atan2, atan2f, atan2l \- arc tangent function of two variables
40 .BI "double atan2(double " y ", double " x );
41 .BI "float atan2f(float " y ", float " x );
42 .BI "long double atan2l(long double " y ", long double " x );
48 Feature Test Macro Requirements for glibc (see
49 .BR feature_test_macros (7)):
56 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
57 _POSIX_C_SOURCE\ >=\ 200112L;
66 function calculates the principal value of the arc tangent of
68 using the signs of the two arguments to determine
69 the quadrant of the result.
71 On success, these functions return the principal value of the arc tangent of
73 in radians; the return value is in the range [\-pi,\ pi].
79 is less than 0, +pi (\-pi) is returned.
85 is greater than 0, +0 (\-0) is returned.
91 is +0 or \-0, \-pi/2 is returned.
97 is +0 or \-0, pi/2 is returned.
102 .\" is 0, a pole error shall not occur.
108 is NaN, a NaN is returned.
111 .\" If the result underflows, a range error may occur and
113 .\" should be returned.
119 is \-0, +pi (\-pi) is returned.
125 is +0, +0 (\-0) is returned.
129 is a finite value greater (less) than 0, and
131 is negative infinity, +pi (\-pi) is returned.
135 is a finite value greater (less) than 0, and
137 is positive infinity, +0 (\-0) is returned.
141 is positive infinity (negative infinity), and
144 pi/2 (\-pi/2) is returned.
148 is positive infinity (negative infinity) and
150 is negative infinity, +3*pi/4 (-3*pi/4) is returned.
154 is positive infinity (negative infinity) and
156 is positive infinity, +pi/4 (-pi/4) is returned.
159 .\" If both arguments are 0, a domain error shall not occur.
162 .\" POSIX.1 documents an optional underflow error
163 .\" glibc 2.8 does not do this.
166 The variant returning