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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
       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 + i * csqrt(1 - z * z))
VERSIONS
       These functions first appeared in glibc in version 2.1.
CONFORMING TO
       C99.
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
       This  page  is  part of release 3.53 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/.

                                  2011-09-15                          CACOS(3)