# cacosh(), cacoshf(), cacoshl()

Compute the complex inverse hyperbolic cosine

## Synopsis:

```#include <complex.h>

double complex cacosh( double complex z );

float complex cacoshf( float complex z );

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

## Arguments:

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

## Library:

libm

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

## Description:

These functions compute the complex inverse hyperbolic cosine of z, with a branch cut at values less than 1 along the real axis.

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

• Call feclearexcept(FE_ALL_EXCEPT) before calling cacosh(), cacoshf(), or cacoshl().
• On return, if fetestexcept(FE_ALL_EXCEPT) is nonzero, then an error has occurred.

## Returns:

The complex inverse hyperbolic cosine of z in the interval [0; Inf) along the real axis and in the interval [−iπ; +iπ] along the imaginary axis.

If z is: These functions return: Errors:
±0 + 0i 0 + (π/2)i
x + Infi, for any finite x Inf + (π/2)i
x + NaNi, for any nonzero finite x NaN + NaNi
0 + NaNi NaN + NaNi
-Inf + yi, for any positive finite y Inf + πi
-Inf - yi, for any positive finite y Inf - πi
-Inf + Infi Inf + (3π/4)i
±Inf + NaNi Inf + NaNi
NaN + yi, for any finite y NaN + NaNi
NaN + Infi Inf + NaNi
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