xref: /freebsd/lib/msun/man/acos.3 (revision 6990ffd8a95caaba6858ad44ff1b3157d1efba8f)
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32.\"     from: @(#)acos.3	5.1 (Berkeley) 5/2/91
33.\" $FreeBSD$
34.\"
35.Dd May 2, 1991
36.Dt ACOS 3
37.Os
38.Sh NAME
39.Nm acos ,
40.Nm acosf
41.Nd arc cosine functions
42.Sh SYNOPSIS
43.Fd #include <math.h>
44.Ft double
45.Fn acos "double x"
46.Ft float
47.Fn acosf "float x"
48.Sh DESCRIPTION
49The
50.Fn acos
51and the
52.Fn acosf
53functions compute the principal value of the arc cosine of
54.Fa x .
55A domain error occurs for arguments not in the range [-1, +1].
56For a discussion of error due to roundoff, see
57.Xr math 3 .
58.Sh RETURN VALUES
59The
60.Fn acos
61and the
62.Fn acosf
63functions return the arc cosine in the range
64.Bq 0 , \*(Pi
65radians.
66On the
67.Tn VAX
68and
69.Tn Tahoe ,
70if:
71.Bd -unfilled -offset indent
72.Pf \&| Ns Ar x Ns \&| > 1 ,
73.Ed
74.Pp
75.Fn acos x
76sets the global variable
77.Va errno
78to
79.Er EDOM
80and a reserved operand fault is generated.
81.Sh SEE ALSO
82.Xr asin 3 ,
83.Xr atan 3 ,
84.Xr atan2 3 ,
85.Xr cos 3 ,
86.Xr cosh 3 ,
87.Xr math 3 ,
88.Xr sin 3 ,
89.Xr sinh 3 ,
90.Xr tan 3 ,
91.Xr tanh 3
92.Sh STANDARDS
93The
94.Fn acos
95function conforms to
96.St -isoC .
97