'\" t
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
.\" <mtk.manpages@gmail.com>
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.\" 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 (date) "Linux man-pages (unreleased)"
.SH NAME
cosh, coshf, coshl \- hyperbolic cosine function
.SH LIBRARY
Math library
.RI ( libm ", " \-lm )
.SH SYNOPSIS
.nf
.B #include <math.h>
.P
.BI "double cosh(double " x );
.BI "float coshf(float " x );
.BI "long double coshl(long double " x );
.fi
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.BR coshf (),
.BR coshl ():
.nf
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.fi
.SH DESCRIPTION
These functions return the hyperbolic cosine of
.IR x ,
which is defined mathematically as:
.P
.in +4n
.EX
cosh(x) = (exp(x) + exp(\-x)) / 2
.EE
.in
.SH RETURN VALUE
On success, these functions return the hyperbolic cosine of
.IR x .
.P
If
.I x
is a NaN, a NaN is returned.
.P
If
.I x
is +0 or \-0, 1 is returned.
.P
If
.I x
is positive infinity or negative infinity,
positive infinity is returned.
.P
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.
.P
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 ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface Attribute Value
T{
.na
.nh
.BR cosh (),
.BR coshf (),
.BR coshl ()
T} Thread safety MT-Safe
.TE
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
C99, POSIX.1-2001.
.P
The variant returning
.I double
also conforms to
SVr4, 4.3BSD.
.SH BUGS
In glibc 2.3.4 and earlier,
an overflow floating-point
.RB ( FE_OVERFLOW )
exception is not raised when an overflow occurs.
.SH SEE ALSO
.BR acosh (3),
.BR asinh (3),
.BR atanh (3),
.BR ccos (3),
.BR sinh (3),
.BR tanh (3)
