[thirdparty/man-pages.git] / man3 / atan2.3

.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
.\"     <mtk.manpages@gmail.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.\" manual page may be incorrect or out-of-date.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'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)
.\"
.TH ATAN2 3  2017-09-15 "" "Linux Programmer's Manual"
.SH NAME
atan2, atan2f, atan2l \- arc tangent function of two variables
.SH SYNOPSIS
.nf
.B #include <math.h>
.PP
.BI "double atan2(double " y ", double " x );
.BI "float atan2f(float " y ", float " x );
.BI "long double atan2l(long double " y ", long double " x );
.fi
.PP
Link with \fI\-lm\fP.
.PP
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.PP
.ad l
.BR atan2f (),
.BR atan2l ():
.RS
_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
    || /* Since glibc 2.19: */ _DEFAULT_SOURCE
    || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.RE
.ad b
.SH DESCRIPTION
These functions calculate the principal value of the arc tangent of
.IR y/x ,
using the signs of the two arguments to determine
the quadrant of the result.
.SH RETURN VALUE
On success, these functions return the principal value of the arc tangent of
.IR y/x
in radians; the return value is in the range [\-pi,\ pi].
.PP
If
.I y
is +0 (\-0) and
.I x
is less than 0, +pi (\-pi) is returned.
.PP
If
.I y
is +0 (\-0) and
.I x
is greater than 0, +0 (\-0) is returned.
.PP
If
.I y
is less than 0 and
.I x
is +0 or \-0, \-pi/2 is returned.
.PP
If
.I y
is greater than 0 and
.I x
is +0 or \-0, pi/2 is returned.
.PP
.\" POSIX.1 says:
.\" If
.\" .I x
.\" is 0, a pole error shall not occur.
.\"
If either
.I x
or
.I y
is NaN, a NaN is returned.
.PP
.\" POSIX.1 says:
.\" If the result underflows, a range error may occur and
.\" .I y/x
.\" should be returned.
.\"
If
.I y
is +0 (\-0) and
.I x
is \-0, +pi (\-pi) is returned.
.PP
If
.I y
is +0 (\-0) and
.I x
is +0, +0 (\-0) is returned.
.PP
If
.I y
is a finite value greater (less) than 0, and
.I x
is negative infinity, +pi (\-pi) is returned.
.PP
If
.I y
is a finite value greater (less) than 0, and
.I x
is positive infinity, +0 (\-0) is returned.
.PP
If
.I y
is positive infinity (negative infinity), and
.I x
is finite,
pi/2 (\-pi/2) is returned.
.PP
If
.I y
is positive infinity (negative infinity) and
.I x
is negative infinity, +3*pi/4 (\-3*pi/4) is returned.
.PP
If
.I y
is positive infinity (negative infinity) and
.I x
is positive infinity, +pi/4 (\-pi/4) is returned.
.\"
.\" POSIX.1 says:
.\" If both arguments are 0, a domain error shall not occur.
.SH ERRORS
No errors occur.
.\" POSIX.1 documents an optional underflow error
.\" glibc 2.8 does not do this.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbw28 lb lb
l l l.
Interface	Attribute	Value
T{
.BR atan2 (),
.BR atan2f (),
.BR atan2l ()
T}	Thread safety	MT-Safe
.TE
.SH CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.
.PP
The variant returning
.I double
also conforms to
SVr4, 4.3BSD, C89.
.SH SEE ALSO
.BR acos (3),
.BR asin (3),
.BR atan (3),
.BR carg (3),
.BR cos (3),
.BR sin (3),
.BR tan (3)
Commit	Line	Data
	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>
	4	.\"
	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
	8	.\" preserved on all copies.
	9	.\"
	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.
	14	.\"
	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
	21	.\" professionally.
	22	.\"
	23	.\" Formatted or processed versions of this manual, if unaccompanied by
	24	.\" the source, must acknowledge the copyright and authors of this work.
	25	.\" %%%LICENSE_END
	26	.\"
	27	.\" References consulted:
	28	.\" Linux libc source code
	29	.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
	30	.\" 386BSD man pages
	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)
	34	.\"
	35	.TH ATAN2 3 2017-09-15 "" "Linux Programmer's Manual"
	36	.SH NAME
	37	atan2, atan2f, atan2l \- arc tangent function of two variables
	38	.SH SYNOPSIS
	39	.nf
	40	.B #include <math.h>
	41	.PP
	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 );
	45	.fi
	46	.PP
	47	Link with \fI\-lm\fP.
	48	.PP
	49	.in -4n
	50	Feature Test Macro Requirements for glibc (see
	51	.BR feature_test_macros (7)):
	52	.in
	53	.PP
	54	.ad l
	55	.BR atan2f (),
	56	.BR atan2l ():
	57	.RS
	58	_ISOC99_SOURCE \|\| _POSIX_C_SOURCE\ >=\ 200112L
	59	\|\| /* Since glibc 2.19: */ _DEFAULT_SOURCE
	60	\|\| /* Glibc versions <= 2.19: */ _BSD_SOURCE \|\| _SVID_SOURCE
	61	.RE
	62	.ad b
	63	.SH DESCRIPTION
	64	These functions calculate the principal value of the arc tangent of
	65	.IR y/x ,
	66	using the signs of the two arguments to determine
	67	the quadrant of the result.
	68	.SH RETURN VALUE
	69	On success, these functions return the principal value of the arc tangent of
	70	.IR y/x
	71	in radians; the return value is in the range [\-pi,\ pi].
	72	.PP
	73	If
	74	.I y
	75	is +0 (\-0) and
	76	.I x
	77	is less than 0, +pi (\-pi) is returned.
	78	.PP
	79	If
	80	.I y
	81	is +0 (\-0) and
	82	.I x
	83	is greater than 0, +0 (\-0) is returned.
	84	.PP
	85	If
	86	.I y
	87	is less than 0 and
	88	.I x
	89	is +0 or \-0, \-pi/2 is returned.
	90	.PP
	91	If
	92	.I y
	93	is greater than 0 and
	94	.I x
	95	is +0 or \-0, pi/2 is returned.
	96	.PP
	97	.\" POSIX.1 says:
	98	.\" If
	99	.\" .I x
	100	.\" is 0, a pole error shall not occur.
	101	.\"
	102	If either
	103	.I x
	104	or
	105	.I y
	106	is NaN, a NaN is returned.
	107	.PP
	108	.\" POSIX.1 says:
	109	.\" If the result underflows, a range error may occur and
	110	.\" .I y/x
	111	.\" should be returned.
	112	.\"
	113	If
	114	.I y
	115	is +0 (\-0) and
	116	.I x
	117	is \-0, +pi (\-pi) is returned.
	118	.PP
	119	If
	120	.I y
	121	is +0 (\-0) and
	122	.I x
	123	is +0, +0 (\-0) is returned.
	124	.PP
	125	If
	126	.I y
	127	is a finite value greater (less) than 0, and
	128	.I x
	129	is negative infinity, +pi (\-pi) is returned.
	130	.PP
	131	If
	132	.I y
	133	is a finite value greater (less) than 0, and
	134	.I x
	135	is positive infinity, +0 (\-0) is returned.
	136	.PP
	137	If
	138	.I y
	139	is positive infinity (negative infinity), and
	140	.I x
	141	is finite,
	142	pi/2 (\-pi/2) is returned.
	143	.PP
	144	If
	145	.I y
	146	is positive infinity (negative infinity) and
	147	.I x
	148	is negative infinity, +3pi/4 (\-3pi/4) is returned.
	149	.PP
	150	If
	151	.I y
	152	is positive infinity (negative infinity) and
	153	.I x
	154	is positive infinity, +pi/4 (\-pi/4) is returned.
	155	.\"
	156	.\" POSIX.1 says:
	157	.\" If both arguments are 0, a domain error shall not occur.
	158	.SH ERRORS
	159	No errors occur.
	160	.\" POSIX.1 documents an optional underflow error
	161	.\" glibc 2.8 does not do this.
	162	.SH ATTRIBUTES
	163	For an explanation of the terms used in this section, see
	164	.BR attributes (7).
	165	.TS
	166	allbox;
	167	lbw28 lb lb
	168	l l l.
	169	Interface Attribute Value
	170	T{
	171	.BR atan2 (),
	172	.BR atan2f (),
	173	.BR atan2l ()
	174	T} Thread safety MT-Safe
	175	.TE
	176	.SH CONFORMING TO
	177	C99, POSIX.1-2001, POSIX.1-2008.
	178	.PP
	179	The variant returning
	180	.I double
	181	also conforms to
	182	SVr4, 4.3BSD, C89.
	183	.SH SEE ALSO
	184	.BR acos (3),
	185	.BR asin (3),
	186	.BR atan (3),
	187	.BR carg (3),
	188	.BR cos (3),
	189	.BR sin (3),
	190	.BR tan (3)