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.

EXAMPLES

/* 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); }

COLOPHON

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