# catanh(), catanhf(), catanhl()

Compute the complex inverse hyperbolic tangent

## Synopsis:

```#include <complex.h>

double complex catanh( double complex z );

float complex catanhf( float complex z );

long double complex catanhl( long double complex z );
```

## Arguments:

z
The value that you want to get the complex inverse hyperbolic tangent of.

## Library:

libm

Use the -l m option to qcc to link against this library.

## Description:

These functions compute the complex inverse hyperbolic tangent of z, with branch cuts outside the interval [−1; +1] along the real axis.

To check for error situations, use feclearexcept() and fetestexcept(). For example:

• Call feclearexcept(FE_ALL_EXCEPT) before calling catanh(), catanhf(), or catanhl().
• On return, if fetestexcept(FE_ALL_EXCEPT) is nonzero, then an error has occurred.

## Returns:

The complex inverse hyperbolic tangent of z, in the range of a half-strip mathematically unbounded along the real axis and in the interval [−iπ/2; +iπ/2] along the imaginary axis.

If z is: These functions return: Errors:
0 + 0i 0 + 0i
0 + NaNi 0 + NaNi
1 + 0i Inf + 0i FE_DIVBYZERO
x + Infi, for any finite positive x 0 + (π/2)i
x + NaNi, for any finite nonzero x NaN + NaNi
Inf + yi, for any finite positive y 0 + (π/2)i
Inf + Infi 0 + (π/2)i
Inf + NaNi 0 + NaNi
NaN + yi, for any finite y NaN + NaNi
NaN + Infi ±0 + (π/2)i, where the sign of the real part is unspecified
NaN + NaNi NaN + NaNi

These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.

## Classification:

Safety:
Cancellation point No
Interrupt handler No
Signal handler No