man3/carg.3

   1 .\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
   2 .\"
   3 .\" SPDX-License-Identifier: GPL-1.0-or-later
   4 .\"
   5 .TH CARG 3 2021-03-22 "" "Linux Programmer's Manual"
   6 .SH NAME
   7 carg, cargf, cargl \- calculate the complex argument
   8 .SH LIBRARY
   9 Math library
  10 .RI ( libm ", " \-lm )
  11 .SH SYNOPSIS
  12 .nf
  13 .B #include <complex.h>
  14 .PP
  15 .BI "double carg(double complex " z ");"
  16 .BI "float cargf(float complex " z ");"
  17 .BI "long double cargl(long double complex " z ");"
  18 .fi
  19 .SH DESCRIPTION
  20 These functions calculate the complex argument (also called phase angle) of
  21 .IR z ,
  22 with a branch cut along the negative real axis.
  23 .PP
  24 A complex number can be described by two real coordinates.
  25 One may use rectangular coordinates and gets
  26 .PP
  27 .nf
  28     z = x + I * y
  29 .fi
  30 .PP
  31 where
  32 .IR "x\ =\ creal(z)"
  33 and
  34 .IR "y\ =\ cimag(z)" .
  35 .PP
  36 Or one may use polar coordinates and gets
  37 .PP
  38 .nf
  39     z = r * cexp(I * a)
  40 .fi
  41 .PP
  42 where
  43 .IR "r\ =\ cabs(z)"
  44 is the "radius", the "modulus", the absolute value of
  45 .IR z ,
  46 and
  47 .IR "a\ =\ carg(z)"
  48 is the "phase angle", the argument of
  49 .IR z .
  50 .PP
  51 One has:
  52 .PP
  53 .nf
  54     tan(carg(z)) = cimag(z) / creal(z)
  55 .fi
  56 .SH RETURN VALUE
  57 The return value is in the range of [\-pi,pi].
  58 .SH VERSIONS
  59 These functions first appeared in glibc in version 2.1.
  60 .SH ATTRIBUTES
  61 For an explanation of the terms used in this section, see
  62 .BR attributes (7).
  63 .ad l
  64 .nh
  65 .TS
  66 allbox;
  67 lbx lb lb
  68 l l l.
  69 Interface       Attribute       Value
  70 T{
  71 .BR carg (),
  72 .BR cargf (),
  73 .BR cargl ()
  74 T}      Thread safety   MT-Safe
  75 .TE
  76 .hy
  77 .ad
  78 .sp 1
  79 .SH CONFORMING TO
  80 C99, POSIX.1-2001, POSIX.1-2008.
  81 .SH SEE ALSO
  82 .BR cabs (3),
  83 .BR complex (7)