xref: /freebsd/lib/msun/man/acos.3 (revision a220d00e74dd245b4fca59c5eca0c53963686325)
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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 LIBRARY
43.Lb libm
44.Sh SYNOPSIS
45.In math.h
46.Ft double
47.Fn acos "double x"
48.Ft float
49.Fn acosf "float x"
50.Sh DESCRIPTION
51The
52.Fn acos
53and the
54.Fn acosf
55functions compute the principal value of the arc cosine of
56.Fa x .
57A domain error occurs for arguments not in the range
58.Bq -1 , +1 .
59For a discussion of error due to roundoff, see
60.Xr math 3 .
61.Sh RETURN VALUES
62The
63.Fn acos
64and the
65.Fn acosf
66functions return the arc cosine in the range
67.Bq 0 , \*(Pi
68radians.
69On the
70.Tn VAX
71and
72.Tn Tahoe ,
73if:
74.Bd -unfilled -offset indent
75.Pf \&| Ns Ar x Ns \&| > 1 ,
76.Ed
77.Pp
78.Fn acos x
79sets the global variable
80.Va errno
81to
82.Er EDOM
83and a reserved operand fault is generated.
84.Sh SEE ALSO
85.Xr asin 3 ,
86.Xr atan 3 ,
87.Xr atan2 3 ,
88.Xr cos 3 ,
89.Xr cosh 3 ,
90.Xr math 3 ,
91.Xr sin 3 ,
92.Xr sinh 3 ,
93.Xr tan 3 ,
94.Xr tanh 3
95.Sh STANDARDS
96The
97.Fn acos
98function conforms to
99.St -isoC .
100