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);
Note
Link with −lm.
DESCRIPTION
The atan2() function
calculates the arc tangent of the two variables x and y. It is similar to calculating
the arc tangent of y /
x, except that the signs of both arguments are
used to determine the quadrant of the result.
RETURN VALUE
The atan2() function returns
the result in radians, which is between −PI and PI
(inclusive).
CONFORMING TO
SVr4, POSIX.1-2001, 4.3BSD, C89. The float and long double
variants are C99 requirements.
This page is part of release 2.79 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man-pages/.
Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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
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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manual page may be incorrect or out-of-date.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.
References consulted:
Linux libc source code
Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
386BSD man pages
Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
Modified 2002-07-27 by Walter Harms
(walter.harms@informatik.uni-oldenburg.de)
![[Note]](../stylesheet/note.png)