CACOS(3)                  (2020-06-09)                   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 cho-
          sen 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.

     EXAMPLES
          /* 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);

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     CACOS(3)                  (2020-06-09)                   CACOS(3)

              }

              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 5.10 of the Linux man-pages
          project.  A 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/.

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