CACOS(3)                   Linux Programmer's Manual                  CACOS(3)



NAME
       cacos, cacosf, cacosl - complex arc cosine

SYNOPSIS
       #include <complex.h>

       double complex cacos(double complex z);
       float complex cacosf(float complex z);
       long double complex cacosl(long double complex z);

       Link with -lm.

DESCRIPTION
       These   functions   calculate   the   complex  arc  cosine  of  z.   If
       y = cacos(z), then z = ccos(y).  The real part of y is  chosen  in  the
       interval [0,pi].

       One has:

           cacos(z) = -i * clog(z + i * csqrt(1 - z * z))

VERSIONS
       These functions first appeared in glibc in version 2.1.

ATTRIBUTES
       For   an   explanation   of   the  terms  used  in  this  section,  see
       attributes(7).

       allbox; lbw28 lb lb  l  l  l.   Interface Attribute Value  T{  cacos(),
       cacosf(), cacosl() T}   Thread safety  MT-Safe

CONFORMING TO
       C99, POSIX.1-2001, POSIX.1-2008.

EXAMPLE
       /* Link with "-lm" */

       #include  <complex.h>  #include <stdlib.h> #include <unistd.h> #include
       <stdio.h>

       int main(int argc, char *argv[]) {
           double complex z, c, f;
           double complex i = I;

           if (argc != 3) {
               fprintf(stderr, "Usage: %s <real> <imag>\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           z = atof(argv[1]) + atof(argv[2]) * I;

           c = cacos(z);

           printf("cacos() = %6.3f %6.3f*i\n", creal(c), cimag(c));

           f = -i * clog(z + i * csqrt(1 - z * z));

           printf("formula = %6.3f %6.3f*i\n", creal(f), cimag(f));

           exit(EXIT_SUCCESS); }

SEE ALSO
       ccos(3), clog(3), complex(7)

COLOPHON
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       description  of  the project, information about reporting bugs, and the
       latest    version    of    this    page,    can     be     found     at
       https://www.kernel.org/doc/man-pages/.



                                  2015-04-19                          CACOS(3)