`atanh`

, `atanhf`

---inverse hyperbolic tangent#include <math.h> double atanh(doublex); float atanhf(floatx);

**Description**

`atanh`

calculates the inverse hyperbolic tangent of `x`.

`atanhf`

is identical, other than taking and returning
`float`

values.

**Returns**

`atanh`

and `atanhf`

return the calculated value.

If
is greater than 1, the global `errno`

is set to `EDOM`

and
the result is a NaN. A `DOMAIN error`

is reported.

If
is 1, the global `errno`

is set to `EDOM`

; and the result is
infinity with the same sign as `x`

. A `SING error`

is reported.

You can modify the error handling for these routines using
`matherr`

.

**Portability**

Neither `atanh`

nor `atanhf`

are ANSI C.

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