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
 | 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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