carg, cargf, cargl - calculate the complex argument

**#include <complex.h>**

**double carg(double complex **`z`

**);**

**float cargf(float complex **`z`

**);**

**long double cargl(long double complex **`z`

**);**

Link with `-lm`

.

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)`

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

These functions first appeared in glibc in version 2.1.

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

Interface | Attribute | Value |

carg(), cargf(), cargl() | Thread safety | MT-Safe |

C99, POSIX.1-2001, POSIX.1-2008.

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