man3/cacos.3

   1 .\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
   2 .\" and Copyright (C) 2011 Michael Kerrisk <mtk.manpages@gmail.com>
   3 .\"
   4 .\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
   5 .\" Distributed under GPL
   6 .\" %%%LICENSE_END
   7 .\"
   8 .TH CACOS 3 2019-03-06 "" "Linux Programmer's Manual"
   9 .SH NAME
  10 cacos, cacosf, cacosl \- complex arc cosine
  11 .SH SYNOPSIS
  12 .B #include <complex.h>
  13 .PP
  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 .PP
  20 Link with \fI\-lm\fP.
  21 .SH DESCRIPTION
  22 These functions calculate the complex arc cosine of
  23 .IR z .
  24 If \fIy\ =\ cacos(z)\fP, then \fIz\ =\ ccos(y)\fP.
  25 The real part of
  26 .I y
  27 is chosen in the interval [0,pi].
  28 .PP
  29 One has:
  30 .PP
  31 .nf
  32     cacos(z) = \-i * clog(z + i * csqrt(1 \- z * z))
  33 .fi
  34 .SH VERSIONS
  35 These functions first appeared in glibc in version 2.1.
  36 .SH ATTRIBUTES
  37 For an explanation of the terms used in this section, see
  38 .BR attributes (7).
  39 .TS
  40 allbox;
  41 lbw28 lb lb
  42 l l l.
  43 Interface       Attribute       Value
  44 T{
  45 .BR cacos (),
  46 .BR cacosf (),
  47 .BR cacosl ()
  48 T}      Thread safety   MT-Safe
  49 .TE
  50 .SH CONFORMING TO
  51 C99, POSIX.1-2001, POSIX.1-2008.
  52 .SH EXAMPLE
  53 .EX
  54 /* Link with "\-lm" */
  55
  56 #include <complex.h>
  57 #include <stdlib.h>
  58 #include <unistd.h>
  59 #include <stdio.h>
  60
  61 int
  62 main(int argc, char *argv[])
  63 {
  64     double complex z, c, f;
  65     double complex i = I;
  66
  67     if (argc != 3) {
  68         fprintf(stderr, "Usage: %s <real> <imag>\en", argv[0]);
  69         exit(EXIT_FAILURE);
  70     }
  71
  72     z = atof(argv[1]) + atof(argv[2]) * I;
  73
  74     c = cacos(z);
  75
  76     printf("cacos() = %6.3f %6.3f*i\en", creal(c), cimag(c));
  77
  78     f = \-i * clog(z + i * csqrt(1 \- z * z));
  79
  80     printf("formula = %6.3f %6.3f*i\en", creal(f), cimag(f));
  81
  82     exit(EXIT_SUCCESS);
  83 }
  84 .EE
  85 .SH SEE ALSO
  86 .BR ccos (3),
  87 .BR clog (3),
  88 .BR complex (7)