---
name: "carg"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/carg"
---

# carg(3)

calculate the complex argument

## NAME

carg, cargf, cargl - calculate the complex argument

## LIBRARY

Math library (*libm*, *-lm*)

## SYNOPSIS

```
#include <complex.h>
```

**double carg(double complex** *z***);** **float cargf(float complex** *z***);** **long double cargl(long double complex** *z***);**

## DESCRIPTION

These functions calculate the complex argument (also called phase angle) of *z*, with a branch cut along the negative real axis.

A complex number can be described by two real coordinates. One may use rectangular coordinates and gets

```
z = x + I * y
```

where *x = creal(z)* and *y = cimag(z)*.

Or one may use polar coordinates and gets

```
z = r * cexp(I * a)
```

where *r = cabs(z)* is the "radius", the "modulus", the absolute value of *z*, and *a = carg(z)* is the "phase angle", the argument of *z*.

One has:

```
tan(carg(z)) = cimag(z) / creal(z)
```

## RETURN VALUE

The return value is in the range of \[-pi,pi\].

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **carg**(), **cargf**(), **cargl**() | Thread safety | MT-Safe |

## STANDARDS

C11, POSIX.1-2008.

## HISTORY

glibc 2.1. C99, POSIX.1-2001.

## SEE ALSO

[**cabs**(3)](/cabs/3.md), [**complex**(7)](/complex/7.md)