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
       The  cacos()  function  calculates  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 + csqrt(z * z - 1))

VERSIONS
       These functions first appeared in glibc in version 2.1.

CONFORMING TO
       C99.

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

COLOPHON
       This  page  is  part of release 3.23 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.