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man:catan

CATAN(3) Linux Programmer's Manual 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);```
`     Link with -lm.`

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 |
+----------------------------+---------------+---------+```

CONFORMING TO

`     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); }`

`     ccos(3), clog(3), ctan(3), complex(7)`
```     This page is part of release 4.16 of the Linux  man-pages  project.   A
`                                2015-04-19                          CATAN(3)`