# TANH

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

ATTRIBUTES

CONFORMING TO

SEE ALSO

COLOPHON

## NAME

tanh, tanhf,
tanhl − hyperbolic tangent function

## SYNOPSIS

**#include
<math.h>**

**double
tanh(double** *x***); **

float tanhf(float *x***); **

long double tanhl(long double *x***);**

Link with
*−lm*.

Feature Test
Macro Requirements for glibc (see
**feature_test_macros**(7)):

**tanhf**(),
**tanhl**():

_BSD_SOURCE || _SVID_SOURCE ||
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;

or *cc -std=c99*

## DESCRIPTION

The
**tanh**() function returns the hyperbolic tangent of
*x*, which is defined mathematically as:

tanh(x) =
sinh(x) / cosh(x)

## RETURN VALUE

On success,
these functions return the hyperbolic tangent of
*x*.

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

If *x* is
+0 (−0), +0 (−0) is returned.

If *x* is
positive infinity (negative infinity), +1 (−1) is
returned.

## ERRORS

No errors
occur.

## ATTRIBUTES

For an
explanation of the terms used in this section, see
**attributes**(7).

## CONFORMING TO

C99,
POSIX.1-2001. The variant returning *double* also
conforms to SVr4, 4.3BSD, C89.

## SEE ALSO

**acosh**(3),
**asinh**(3), **atanh**(3), **cosh**(3),
**ctanh**(3), **sinh**(3)

## COLOPHON

This page is
part of release 3.53 of the Linux *man-pages* project.
A description of the project, and information about
reporting bugs, can be found at
http://www.kernel.org/doc/man−pages/.