1 .\" Copyright (c) 1991 The Regents of the University of California.
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20 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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32 .\" from: @(#)atan.3 5.1 (Berkeley) 5/2/91
33 .\" $FreeBSD: src/lib/msun/man/atan.3,v 1.10 2001/10/13 12:23:22 bde Exp $
34 .\"
35 .Dd May 2, 1991
36 .Dt ATAN 3
37 .Os
38 .Sh NAME
39 .Nm atan ,
40 .Nm atanf
41 .Nd arc tangent functions of one variable
42 .Sh LIBRARY
43 .Lb libm
44 .Sh SYNOPSIS
45 .In math.h
46 .Ft double
47 .Fn atan "double x"
48 .Ft float
49 .Fn atanf "float x"
50 .Sh DESCRIPTION
51 The
52 .Fn atan
53 and the
54 .Fn atanf
55 functions compute the principal value of the arc tangent of
56 .Fa x .
57 For a discussion of error due to roundoff, see
58 .Xr math 3 .
59 .Sh RETURN VALUES
60 The
61 .Fn atan
62 and the
63 .Fn atanf
64 function returns the arc tangent in the range
65 .Bk -words
66 .Bq -\*(Pi/2 , +\*(Pi/2
67 .Ek
68 radians.
69 .Sh SEE ALSO
70 .Xr acos 3 ,
71 .Xr asin 3 ,
72 .Xr atan2 3 ,
73 .Xr cos 3 ,
74 .Xr cosh 3 ,
75 .Xr math 3 ,
76 .Xr sin 3 ,
77 .Xr sinh 3 ,
78 .Xr tan 3 ,
79 .Xr tanh 3
80 .Sh STANDARDS
81 The
82 .Fn atan
83 function conforms to
84 .St -isoC .