May 6, 1991 ATANH 3

### NAME

atanh, atanhf - inverse hyperbolic tangent function

### LIBRARY

Math Library (libm, -lm)

### SYNOPSIS

```double` atanh(```double x`)
```float` atanhf(```float x`)

### DESCRIPTION

The atanh(``) and atanhf(``) functions compute the inverse hyperbolic tangent of the real argument x.

### RETURN VALUES

If |x|1, atanh(```x`) and atanhf(```x`) return +inf, -inf or NaN, and sets the global variable errno to EDOM.

### SEE ALSO

acosh(3), asinh(3), exp(3), math(3)

### HISTORY

The atanh(``) function appeared in 4.3BSD.