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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); }