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 1.3 1993/08/14 13:42:32 mycroft Exp $
34.\"
35.Dd May 2, 1991
36.Dt ATAN2 3
37.Os
38.Sh NAME
39.Nm atan2
40.Nd arc tangent function of two variables
41.Sh SYNOPSIS
42.Fd #include <math.h>
43.Ft double
44.Fn atan2 "double y" "double x"
45.Sh DESCRIPTION
46The
47.Xr atan2
48function computes the principal value of the arc tangent of
49.Ar y/ Ns Ar x ,
50using the signs of both arguments to determine the quadrant of
51the return value.
52.Sh RETURN VALUES
53The
54.Xr atan2
55function, if successful,
56returns the arc tangent of
57.Ar y/ Ns Ar x
58in the range
59.Bk -words
60.Bq \&- Ns \*(Pi , \&+ Ns \*(Pi
61.Ek
62radians.
63If both
64.Ar x
65and
66.Ar y
67are zero, the global variable
68.Va errno
69is set to
70.Er EDOM .
71On the
72.Tn VAX :
73.Bl -column atan_(y,x)_:=____ sign(y)_(Pi_atan2(Xy_xX))___
74.It Fn atan2 y x No := Ta

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