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The functions in this section are related to the exponential functions; see section Exponentiation and Logarithms.

__Function:__ double **sinh** *(double x)*

The `sinh`

function returns the hyperbolic sine of `x`, defined
mathematically as `exp (`

. The
function fails, and sets `x`) - exp (-`x`) / 2`errno`

to `ERANGE`

, if the value of
`x` is too large; that is, if overflow occurs.

__Function:__ double **cosh** *(double x)*

The `cosh`

function returns the hyperbolic cosine of `x`,
defined mathematically as `exp (`

.
The function fails, and sets `x`) + exp (-`x`) / 2`errno`

to `ERANGE`

, if the value
of `x` is too large; that is, if overflow occurs.

__Function:__ double **tanh** *(double x)*

This function returns the hyperbolic tangent of `x`, whose
mathematical definition is `sinh (`

.
`x`) / cosh (`x`)

__Function:__ double **asinh** *(double x)*

This function returns the inverse hyperbolic sine of `x`---the
value whose hyperbolic sine is `x`.

__Function:__ double **acosh** *(double x)*

This function returns the inverse hyperbolic cosine of `x`---the
value whose hyperbolic cosine is `x`. If `x` is less than
`1`

, `acosh`

returns `HUGE_VAL`

.

__Function:__ double **atanh** *(double x)*

This function returns the inverse hyperbolic tangent of `x`---the
value whose hyperbolic tangent is `x`. If the absolute value of
`x` is greater than or equal to `1`

, `atanh`

returns
`HUGE_VAL`

.

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