NAME

cacos, cacosf, cacosl - complex arc cosine

LIBRARY

Math library (libm, -lm)

SYNOPSIS

#include <complex.h>

double complex cacos(double complex z);
float complex cacosf(float complex z);
long double complex cacosl(long double complex z);

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 were added in glibc 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

STANDARDS

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

EXAMPLES

/* Link with "-lm" */
#include <complex.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.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);
}