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#### 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

```       The   catanh()   function  calculates  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.

```

#### CONFORMINGTO

```       C99.

```

#### 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 3.35 of the Linux man-pages project.  A description of the
project, and information about reporting bugs, can be found at  http://man7.org/linux/man-
pages/.

2011-09-15                                  CATANH(3)
```