Section (3) atan2
Name
atan2, atan2f, atan2l — arc tangent function of two variables
Synopsis
#include <math.h>
double
atan2( |
double y, |
double x) ; |
float
atan2f( |
float y, |
float x) ; |
long double
atan2l( |
long double y, |
long double x) ; |
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DESCRIPTION
These functions calculate the principal value of the arc
tangent of y/x
, using the signs
of the two arguments to determine the quadrant of the
result.
RETURN VALUE
On success, these functions return the principal value of
the arc tangent of y/x
in
radians; the return value is in the range [−pi,
pi].
If y
is +0
(−0) and x
is
less than 0, +pi (−pi) is returned.
If y
is +0
(−0) and x
is
greater than 0, +0 (−0) is returned.
If y
is less than
0 and x
is +0 or
−0, −pi/2 is returned.
If y
is greater
than 0 and x
is +0 or
−0, pi/2 is returned.
If either x
or
y
is NaN, a NaN is
returned.
If y
is +0
(−0) and x
is
−0, +pi (−pi) is returned.
If y
is +0
(−0) and x
is
+0, +0 (−0) is returned.
If y
is a finite
value greater (less) than 0, and x
is negative infinity, +pi
(−pi) is returned.
If y
is a finite
value greater (less) than 0, and x
is positive infinity, +0
(−0) is returned.
If y
is positive
infinity (negative infinity), and x
is finite, pi/2 (−pi/2)
is returned.
If y
is positive
infinity (negative infinity) and x
is negative infinity, +3*pi/4
(−3*pi/4) is returned.
If y
is positive
infinity (negative infinity) and x
is positive infinity, +pi/4
(−pi/4) is returned.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
Interface | Attribute | Value |
atan2 (), atan2f (), atan2l () |
Thread safety | MT-Safe |
CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning double also conforms to SVr4, 4.3BSD, C89.
COLOPHON
This page is part of release 4.16 of the Linux man-pages
project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
Copyright 1993 David Metcalfe (davidprism.demon.co.uk) and Copyright 2008, Linux Foundation, written by Michael Kerrisk <mtk.manpagesgmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END References consulted: Linux libc source code Lewine_zsingle_quotesz_s _POSIX Programmer_zsingle_quotesz_s Guide_ (O_zsingle_quotesz_Reilly & Associates, 1991) 386BSD man pages Modified 1993-07-24 by Rik Faith (faithcs.unc.edu) Modified 2002-07-27 by Walter Harms (walter.harmsinformatik.uni-oldenburg.de) |