# CATANH

NAME
SYNOPSIS
DESCRIPTION
VERSIONS
ATTRIBUTES
CONFORMING TO
EXAMPLE
COLOPHON

## 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.

## ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7). C99.

## EXAMPLE

#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);
exit(EXIT_FAILURE);
}

z = atof(argv) + atof(argv) * 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);
}