1.\" Copyright (c) 1991 The Regents of the University of California.
2.\" All rights reserved.
3.\"
4.\" Redistribution and use in source and binary forms, with or without
5.\" modification, are permitted provided that the following conditions
6.\" are met:
7.\" 1. Redistributions of source code must retain the above copyright
8.\" notice, this list of conditions and the following disclaimer.

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25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30.\" SUCH DAMAGE.
31.\"
32.\" from: @(#)atan2.3 5.1 (Berkeley) 5/2/91
33.\" $Id: atan2.3,v 1.1.1.1 1994/08/19 09:39:41 jkh Exp $
34.\"
35.Dd May 2, 1991
36.Dt ATAN2 3
37.Os
38.Sh NAME
39.Nm atan2 ,
40.Nm atan2f
41.Nd arc tangent functions of two variables
42.Sh SYNOPSIS
43.Fd #include <math.h>
44.Ft double
45.Fn atan2 "double y" "double x"
46.Ft float
47.Fn atan2f "float y" "float x"
48.Sh DESCRIPTION
49The
50.Fn atan2
51and the
52.Fn atan2f
53functions compute the principal value of the arc tangent of
54.Fa y/ Ns Ar x ,
55using the signs of both arguments to determine the quadrant of
56the return value.
57.Sh RETURN VALUES
58The
59.Fn atan2
60and the
61.Fn atan2f
62functions, if successful,
63return the arc tangent of
64.Fa y/ Ns Ar x
65in the range
66.Bk -words
67.Bq \&- Ns \*(Pi , \&+ Ns \*(Pi
68.Ek
69radians.
70If both
71.Fa x
72and
73.Fa y
74are zero, the global variable
75.Va errno
76is set to
77.Er EDOM .
78On the
79.Tn VAX :
80.Bl -column atan_(y,x)_:=____ sign(y)_(Pi_atan2(Xy_xX))___
81.It Fn atan2 y x No := Ta

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