man3/carg.3

   1 .\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
   2 .\"
   3 .\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
   4 .\" Distributed under GPL
   5 .\" %%%LICENSE_END
   6 .\"
   7 .TH CARG 3 2017-09-15 "" "Linux Programmer's Manual"
   8 .SH NAME
   9 carg, cargf, cargl \- calculate the complex argument
  10 .SH SYNOPSIS
  11 .B #include <complex.h>
  12 .PP
  13 .BI "double carg(double complex " z ");"
  14 .br
  15 .BI "float cargf(float complex " z ");"
  16 .br
  17 .BI "long double cargl(long double complex " z ");"
  18 .PP
  19 Link with \fI\-lm\fP.
  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 .nf
  29     z = x + I * y
  30 .fi
  31 .PP
  32 where
  33 .IR "x\ =\ creal(z)"
  34 and
  35 .IR "y\ =\ cimag(z)" .
  36 .PP
  37 Or one may use polar coordinates and gets
  38 .PP
  39 .nf
  40     z = r * cexp(I * a)
  41 .fi
  42 .PP
  43 where
  44 .IR "r\ =\ cabs(z)"
  45 is the "radius", the "modulus", the absolute value of
  46 .IR z ,
  47 and
  48 .IR "a\ =\ carg(z)"
  49 is the "phase angle", the argument of
  50 .IR z .
  51 .PP
  52 One has:
  53 .PP
  54 .nf
  55     tan(carg(z)) = cimag(z) / creal(z)
  56 .fi
  57 .SH RETURN VALUE
  58 The return value is the range of [\-pi,pi].
  59 .SH VERSIONS
  60 These functions first appeared in glibc in version 2.1.
  61 .SH ATTRIBUTES
  62 For an explanation of the terms used in this section, see
  63 .BR attributes (7).
  64 .TS
  65 allbox;
  66 lbw24 lb lb
  67 l l l.
  68 Interface       Attribute       Value
  69 T{
  70 .BR carg (),
  71 .BR cargf (),
  72 .BR cargl ()
  73 T}      Thread safety   MT-Safe
  74 .TE
  75 .SH CONFORMING TO
  76 C99, POSIX.1-2001, POSIX.1-2008.
  77 .SH SEE ALSO
  78 .BR cabs (3),
  79 .BR complex (7)