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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