mirror of https://github.com/mkerrisk/man-pages
191 lines
4.3 KiB
Groff
191 lines
4.3 KiB
Groff
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
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.\" <mtk.manpages@gmail.com>
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.\" References consulted:
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.\" Linux libc source code
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.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
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.\" 386BSD man pages
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.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
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.\" Modified 2002-07-27 by Walter Harms
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.\" (walter.harms@informatik.uni-oldenburg.de)
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.\"
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.TH ATAN2 3 2017-09-15 "" "Linux Programmer's Manual"
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.SH NAME
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atan2, atan2f, atan2l \- arc tangent function of two variables
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.SH SYNOPSIS
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.nf
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.B #include <math.h>
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.PP
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.BI "double atan2(double " y ", double " x );
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.BI "float atan2f(float " y ", float " x );
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.BI "long double atan2l(long double " y ", long double " x );
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.fi
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.PP
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Link with \fI\-lm\fP.
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.PP
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.RS -4
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.RE
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.PP
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.ad l
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.BR atan2f (),
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.BR atan2l ():
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.RS
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_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
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|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
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|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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.RE
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.ad b
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.SH DESCRIPTION
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These functions calculate the principal value of the arc tangent of
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.IR y/x ,
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using the signs of the two arguments to determine
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the quadrant of the result.
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.SH RETURN VALUE
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On success, these functions return the principal value of the arc tangent of
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.IR y/x
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in radians; the return value is in the range [\-pi,\ pi].
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.PP
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If
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.I y
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is +0 (\-0) and
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.I x
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is less than 0, +pi (\-pi) is returned.
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.PP
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If
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.I y
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is +0 (\-0) and
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.I x
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is greater than 0, +0 (\-0) is returned.
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.PP
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If
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.I y
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is less than 0 and
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.I x
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is +0 or \-0, \-pi/2 is returned.
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.PP
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If
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.I y
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is greater than 0 and
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.I x
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is +0 or \-0, pi/2 is returned.
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.PP
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.\" POSIX.1 says:
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.\" If
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.\" .I x
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.\" is 0, a pole error shall not occur.
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.\"
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If either
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.I x
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or
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.I y
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is NaN, a NaN is returned.
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.PP
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.\" POSIX.1 says:
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.\" If the result underflows, a range error may occur and
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.\" .I y/x
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.\" should be returned.
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.\"
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If
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.I y
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is +0 (\-0) and
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.I x
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is \-0, +pi (\-pi) is returned.
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.PP
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If
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.I y
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is +0 (\-0) and
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.I x
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is +0, +0 (\-0) is returned.
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.PP
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If
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.I y
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is a finite value greater (less) than 0, and
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.I x
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is negative infinity, +pi (\-pi) is returned.
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.PP
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If
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.I y
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is a finite value greater (less) than 0, and
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.I x
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is positive infinity, +0 (\-0) is returned.
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.PP
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If
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.I y
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is positive infinity (negative infinity), and
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.I x
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is finite,
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pi/2 (\-pi/2) is returned.
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.PP
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If
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.I y
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is positive infinity (negative infinity) and
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.I x
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is negative infinity, +3*pi/4 (\-3*pi/4) is returned.
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.PP
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If
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.I y
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is positive infinity (negative infinity) and
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.I x
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is positive infinity, +pi/4 (\-pi/4) is returned.
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.\"
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.\" POSIX.1 says:
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.\" If both arguments are 0, a domain error shall not occur.
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.SH ERRORS
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No errors occur.
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.\" POSIX.1 documents an optional underflow error
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.\" glibc 2.8 does not do this.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.TS
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allbox;
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lbw28 lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR atan2 (),
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.BR atan2f (),
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.BR atan2l ()
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T} Thread safety MT-Safe
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.TE
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.SH CONFORMING TO
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C99, POSIX.1-2001, POSIX.1-2008.
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.PP
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The variant returning
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.I double
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also conforms to
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SVr4, 4.3BSD, C89.
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.SH SEE ALSO
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.BR acos (3),
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.BR asin (3),
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.BR atan (3),
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.BR carg (3),
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.BR cos (3),
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.BR sin (3),
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.BR tan (3)
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