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>
", argv[0]);
	       exit(EXIT_FAILURE);
	   }

	   z = atof(argv[1]) + atof(argv[2]) * I;

	   c = cacos(z);

	   printf("cacos() = %6.3f %6.3f*i
", creal(c), cimag(c));

	   f = -i * clog(z + i * csqrt(1 - z * z));

	   printf("formula = %6.3f %6.3f*i
", creal(f), cimag(f));

	   exit(EXIT_SUCCESS);
       }

SEE ALSO

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

COLOPHON

       This page is part of release 3.44 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)