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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).
       +-----------------------------+---------------+---------+
       |Interface                    | Attribute     | Value   |
       +-----------------------------+---------------+---------+
       |cacos(), cacosf(), cacosl()  | 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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       latest    version    of    this    page,    can     be     found     at
       https://www.kernel.org/doc/man-pages/.
                                  2015-04-19                          CACOS(3)