cacosh(), cacoshf(), cacoshl()

Updated: October 26, 2022

Compute the complex inverse hyperbolic cosine


#include <complex.h>

double complex cacosh( double complex z );

float complex cacoshf( float complex z );

long double complex cacoshl( long double complex z );


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


The general-purpose math library.
(QNX Neutrino 7.1 or later) A library that optimizes the code for ARMv8.2 chips that have Scalable Vector Extension hardware.

Your system requirements will determine how you should work with these libraries:

Note: Compile your program with the -fno-builtin option to prevent the compiler from using a built-in version of the function.


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:


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 ± (π/2)i, where the sign of the imaginary part is unspecified
Inf + Infi Inf + (π/4)i
-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.


C11, POSIX 1003.1

Cancellation point No
Interrupt handler Yes
Signal handler Yes
Thread Yes