# catanh(3)

#### NAME

```   catanh, catanhf, catanhl - complex arc tangents hyperbolic

```

#### SYNOPSIS

```   #include <complex.h>

double complex catanh(double complex z);
float complex catanhf(float complex z);
long double complex catanhl(long double complex z);

```

#### DESCRIPTION

```   These  functions calculate the complex arc hyperbolic tangent of z.  If
y = catanh(z), then z = ctanh(y).  The imaginary part of y is chosen in
the interval [-pi/2,pi/2].

One has:

catanh(z) = 0.5 * (clog(1 + z) - clog(1 - z))

```

#### VERSIONS

```   These functions first appeared in glibc in version 2.1.

```

#### ATTRIBUTES

```   For   an   explanation   of   the  terms  used  in  this  section,  see
attributes(7).

Interface                       Attribute      Value

catanh(), catanhf(), catanhl()  Thread safety  MT-Safe

```

#### CONFORMINGTO

```   C99, POSIX.1-2001, POSIX.1-2008.

```

#### EXAMPLE

```   /* Link with "-lm" */

#include <complex.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>

int
main(int argc, char *argv[])
{
double complex z, c, f;

if (argc != 3) {
fprintf(stderr, "Usage: %s <real> <imag>\n", argv[0]);
exit(EXIT_FAILURE);
}

z = atof(argv[1]) + atof(argv[2]) * I;

c = catanh(z);
printf("catanh() = %6.3f %6.3f*i\n", creal(c), cimag(c));

f = 0.5 * (clog(1 + z) - clog(1 - z));
printf("formula  = %6.3f %6.3f*i\n", creal(f2), cimag(f2));

exit(EXIT_SUCCESS);
}

```

#### SEEALSO

```   atanh(3), cabs(3), cimag(3), ctanh(3), complex(7)

```

#### COLOPHON

```   This page is part of release 4.09 of the Linux  man-pages  project.   A
description  of  the project, information about reporting bugs, and the
latest    version    of    this    page,    can     be     found     at
https://www.kernel.org/doc/man-pages/.

2015-04-19                         CATANH(3)
```

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