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

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                              2015-04-19                          CACOS(3)

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