catan(3)

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);

```

DESCRIPTION

```   These   functions   calculate   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).

Interface                    Attribute      Value

catan(), catanf(), catanl()  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;
double complex i = I;

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

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

```

SEEALSO

```   ccos(3), clog(3), ctan(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                          CATAN(3)
```

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