.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
.\"     <mtk.manpages@gmail.com>
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
.\" Modified 2002-07-25 by Walter Harms
.\" 	(walter.harms@informatik.uni-oldenburg.de)
.\"
.\" Japanese Version Copyright (c) 1996 Kenji Kajiwara and Kentaro Ogawa
.\"         all rights reserved.
.\" Translated Sat, 13 Jul 1996 17:58:16 JST
.\"         by Kenji Kajiwara and Kentaro Ogawa
.\" Proof Reading: Takashi Yoshino
.\" Updated Tue Aug  5 23:16:48 JST 2003
.\"         by Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\" Updated 2008-09-14, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\"
.TH ACOSH 3   2010-09-20 "" "Linux Programmer's Manual"
.\"O .SH NAME
.SH 名前
.\"O acosh, acoshf, acoshl \- inverse hyperbolic cosine function
acosh, acoshf, acoshl \- 逆双曲線余弦（inverse hyperbolic cosine）関数
.\"O .SH SYNOPSIS
.SH 書式
.nf
.B #include <math.h>
.sp
.BI "double acosh(double " x );
.br
.BI "float acoshf(float " x );
.br
.BI "long double acoshl(long double " x );
.sp
.fi
.\"O Link with \fI\-lm\fP.
\fI\-lm\fP でリンクする。
.sp
.in -4n
.\"O Feature Test Macro Requirements for glibc (see
.\"O .BR feature_test_macros (7)):
glibc 向けの機能検査マクロの要件
.RB ( feature_test_macros (7)
参照):
.in
.sp
.ad l
.BR acosh ():
.RS 4
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
_XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE ||
_POSIX_C_SOURCE\ >=\ 200112L;
.br
or
.I cc\ -std=c99
.RE
.br
.BR acoshf (),
.BR acoshl ():
.RS 4
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE\ >=\ 200112L;
.br
or
.I cc\ -std=c99
.RE
.ad b
.\"O .SH DESCRIPTION
.SH 説明
.\"O The
.\"O .BR acosh ()
.\"O function calculates the inverse hyperbolic cosine of
.\"O \fIx\fP; that is the value whose hyperbolic cosine is \fIx\fP.
.BR acosh ()
関数は \fIx\fP の逆双曲線余弦（inverse hyperbolic cosine）を
計算する。
すなわち、その双曲線余弦（hyperbolic cosine）が \fIx\fP に
なるような値である。
.\"O .SH "RETURN VALUE"
.SH 返り値
.\"O On success, these functions return the inverse hyperbolic cosine of
.\"O .IR x .
成功すると、これらの関数は
.I x
の逆双曲線余弦を返す。

.\"O If
.\"O .I x
.\"O is a NaN, a NaN is returned.
.I x
が NaN の場合、NaN が返される。

.\"O If
.\"O .I x
.\"O is +1, +0 is returned.
.I x
が +1 の場合、+0 が返される。

.\"O If
.\"O .I x
.\"O is positive infinity, positive infinity is returned.
.I x
が正の無限大の場合、正の無限大が返される。

.\"O If
.\"O .I x
.\"O is less than 1,
.\"O a domain error occurs,
.\"O and the functions return a NaN.
.I x
が 1 より小さい場合、
領域エラー (domain error) が発生し、NaN が返される。
.\"O .SH ERRORS
.SH エラー
.\"O See
.\"O .BR math_error (7)
.\"O for information on how to determine whether an error has occurred
.\"O when calling these functions.
これらの関数を呼び出した際にエラーが発生したかの判定方法についての情報は
.BR math_error (7)
を参照のこと。
.PP
.\"O The following errors can occur:
以下のエラーが発生する可能性がある。
.TP
.\"O Domain error: \fIx\fP is less than 1
領域エラー (domain error): \fIx\fP が 1 より小さい
.\"O .I errno
.\"O is set to
.\"O .BR EDOM .
.\"O An invalid floating-point exception
.\"O .RB ( FE_INVALID )
.\"O is raised.
.I errno
に
.B EDOM
が設定される。
無効 (invalid) 浮動小数点例外
.RB ( FE_INVALID )
が上がる。
.\"O .SH "CONFORMING TO"
.SH 準拠
C99, POSIX.1-2001.
.\"O The variant returning
.\"O .I double
.\"O also conforms to
.\"O SVr4, 4.3BSD, C89.
.I double
版の関数は SVr4, 4.3BSD, C89 にも準拠している。
.\"O .SH "SEE ALSO"
.SH 関連項目
.BR asinh (3),
.BR atanh (3),
.BR cacosh (3),
.BR cosh (3),
.BR sinh (3),
.BR tanh (3)