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).

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>\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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