NAME | SYNOPSIS | DESCRIPTION | VERSIONS | ATTRIBUTES | CONFORMING TO | EXAMPLE | SEE ALSO | COLOPHON

CACOS(3)                  Linux Programmer's Manual                 CACOS(3)

NAME         top

       cacos, cacosf, cacosl - complex arc cosine

SYNOPSIS         top

       #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         top

       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         top

       These functions first appeared in glibc in version 2.1.

ATTRIBUTES         top

       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         top

       C99, POSIX.1-2001, POSIX.1-2008.

EXAMPLE         top

       /* 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         top

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

COLOPHON         top

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                                 2015-04-19                         CACOS(3)