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
       This page is part of release 4.10 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/.



				  2015-04-19			      CACOS(3)