1994-05-27 05:00:24 +00:00
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.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)acos.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd June 4, 1993
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.Dt ACOS 3
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.Os
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.Sh NAME
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.Nm acos
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.Nd arc cosine function
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.Sh SYNOPSIS
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.Fd #include <math.h>
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.Ft double
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.Fn acos "double x"
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.Sh DESCRIPTION
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The
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.Fn acos
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function computes the principal value of the arc cosine of
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.Fa x .
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A domain error occurs for arguments not in the range [-1, +1].
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For a discussion of error due to roundoff, see
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.Xr math 3 .
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.Sh RETURN VALUES
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The
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.Fn acos
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function returns the arc cosine in the range
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.Bq 0 , \*(Pi
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radians.
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On the
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.Tn VAX
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and
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.Tn Tahoe ,
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if:
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.Bd -unfilled -offset indent
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.Pf \&| Ns Ar x Ns \&| > 1 ,
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.Ed
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.Pp
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.Fn acos x
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sets the global variable
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.Va errno
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to
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.Dv EDOM
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and a reserved operand fault is generated.
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.Sh SEE ALSO
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.Xr asin 3 ,
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.Xr atan 3 ,
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.Xr atan2 3 ,
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1997-01-20 23:23:22 +00:00
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.Xr cos 3 ,
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1994-05-27 05:00:24 +00:00
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.Xr cosh 3 ,
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.Xr math 3 ,
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1997-01-20 23:23:22 +00:00
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.Xr sin 3 ,
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.Xr sinh 3 ,
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.Xr tan 3 ,
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.Xr tanh 3
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1994-05-27 05:00:24 +00:00
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.Sh STANDARDS
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The
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.Fn acos
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function conforms to
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.St -ansiC .
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