man3/carg.3

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