man3/cacos.3

   1 .\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
   2 .\" and Copyright (C) 2011 Michael Kerrisk <mtk.manpages@gamil.com>
   3 .\"
   4 .\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
   5 .\" Distributed under GPL
   6 .\" %%%LICENSE_END
   7 .\"
   8 .TH CACOS 3 2015-03-02 "" "Linux Programmer's Manual"
   9 .SH NAME
  10 cacos, cacosf, cacosl \- complex arc cosine
  11 .SH SYNOPSIS
  12 .B #include <complex.h>
  13 .sp
  14 .BI "double complex cacos(double complex " z );
  15 .br
  16 .BI "float complex cacosf(float complex " z );
  17 .br
  18 .BI "long double complex cacosl(long double complex " z );
  19 .sp
  20 Link with \fI\-lm\fP.
  21 .SH DESCRIPTION
  22 The
  23 .BR cacos ()
  24 function calculates the complex arc cosine of
  25 .IR z .
  26 If \fIy\ =\ cacos(z)\fP, then \fIz\ =\ ccos(y)\fP.
  27 The real part of
  28 .I y
  29 is chosen in the interval [0,pi].
  30 .LP
  31 One has:
  32 .nf
  33
  34     cacos(z) = \-i * clog(z + i * csqrt(1 \- z * z))
  35 .fi
  36 .SH VERSIONS
  37 These functions first appeared in glibc in version 2.1.
  38 .SH ATTRIBUTES
  39 For an explanation of the terms used in this section, see
  40 .BR attributes (7).
  41 .TS
  42 allbox;
  43 lbw28 lb lb
  44 l l l.
  45 Interface       Attribute       Value
  46 T{
  47 .BR cacos (),
  48 .BR cacosf (),
  49 .BR cacosl ()
  50 T}      Thread safety   MT-Safe
  51 .TE
  52 .SH CONFORMING TO
  53 C99, POSIX.1-2001, POSIX.1-2008.
  54 .SH EXAMPLE
  55 .nf
  56 /* Link with "\-lm" */
  57
  58 #include <complex.h>
  59 #include <stdlib.h>
  60 #include <unistd.h>
  61 #include <stdio.h>
  62
  63 int
  64 main(int argc, char *argv[])
  65 {
  66     double complex z, c, f;
  67     double complex i = I;
  68
  69     if (argc != 3) {
  70         fprintf(stderr, "Usage: %s <real> <imag>\\n", argv[0]);
  71         exit(EXIT_FAILURE);
  72     }
  73
  74     z = atof(argv[1]) + atof(argv[2]) * I;
  75
  76     c = cacos(z);
  77
  78     printf("cacos() = %6.3f %6.3f*i\\n", creal(c), cimag(c));
  79
  80     f = \-i * clog(z + i * csqrt(1 \- z * z));
  81
  82     printf("formula = %6.3f %6.3f*i\\n", creal(f), cimag(f));
  83
  84     exit(EXIT_SUCCESS);
  85 }
  86 .fi
  87 .SH SEE ALSO
  88 .BR ccos (3),
  89 .BR clog (3),
  90 .BR complex (7)