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.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
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.\" 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 1996-06-08 by aeb
.\" Modified 2002-07-27 by Walter Harms
.\" (walter.harms@informatik.uni-oldenburg.de)
.\"
.TH COSH 3 2008-08-05 ""  "Linux Programmer's Manual"
.SH NAME
cosh, coshf, coshl \- hyperbolic cosine function
.SH SYNOPSIS
.nf
.B #include <math.h>
.sp
.BI "double cosh(double " x );
.br
.BI "float coshf(float " x );
.br
.BI "long double coshl(long double " x );
.fi
.sp
Link with \fI\-lm\fP.
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.ad l
.BR coshf (),
.BR coshl ():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
.I cc\ -std=c99
.ad b
.SH DESCRIPTION
The
.BR cosh ()
function returns the hyperbolic cosine of \fIx\fP, which
is defined mathematically as:
.nf

    cosh(x) = (exp(x) + exp(\-x)) / 2
.fi
.SH "RETURN VALUE"
On success, these functions return the hyperbolic cosine of
.IR x .

If
.I x
is a NaN, a NaN is returned.

If
.I x
is +0 or \-0, 1 is returned.

If
.I x
is positive infinity or negative infinity,
positive infinity is returned.

If the result overflows,
a "range error" occurs,
and the functions return
.RB + HUGE_VAL ,
.RB + HUGE_VALF ,
or
.RB + HUGE_VALL ,
respectively.
.SH ERRORS
See
.BR math_error (7)
for information on how to determine whether an error has occurred
when calling these functions.
.PP
The following errors can occur:
.TP
Range error: result overflow
.I errno
is set to
.BR ERANGE .
An overflow floating-point exception
.RB ( FE_OVERFLOW )
is raised.
.SH "CONFORMING TO"
C99, POSIX.1-2001.
The variant returning
.I double
also conforms to
SVr4, 4.3BSD.
.SH "SEE ALSO"
.BR acosh (3),
.BR asinh (3),
.BR atanh (3),
.BR ccos (3),
.BR sinh (3),
.BR tanh (3)