carg(3) Library Functions Manual carg(3)

carg, cargf, cargl - calculate the complex argument

Math library (libm, -lm)

#include <complex.h>
double carg(double complex z);
float cargf(float complex z);
long double cargl(long double complex z);

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 in the range of [-pi,pi].

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

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

C11, POSIX.1-2008.

glibc 2.1. C99, POSIX.1-2001.

cabs(3), complex(7)

2024-05-02 Linux man-pages 6.8