# CATAN

NAME
SYNOPSIS
DESCRIPTION
VERSIONS
ATTRIBUTES
CONFORMING TO
EXAMPLE
SEE ALSO
COLOPHON

## NAME

catan, catanf, catanl − complex arc tangents

## SYNOPSIS

#include <complex.h>

double complex catan(double complex z);
float complex catanf(float complex
z);
long double complex catanl(long double complex
z);

Link with −lm.

## DESCRIPTION

The catan() function calculates the complex arc tangent of z. If y = catan(z), then z = ctan(y). The real part of y is chosen in the interval [−pi/2,pi/2].

One has:

catan(z) = (clog(1 + i * z) − clog(1 − i * z)) / (2 * i)

## 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

/* 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;
double complex i = I;

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

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

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

f = (clog(1 + i * z) − clog(1 − i * z)) / (2 * i);
printf("formula = %6.3f %6.3f*i\n", creal(f2), cimag(f2));

exit(EXIT_SUCCESS);
}

## SEE ALSO

ccos(3), clog(3), ctan(3), complex(7)

## COLOPHON

This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man−pages/.