CACOSH(3)

NAME
cacosh, cacoshf, cacoshl - complex arc hyperbolic cosine

SYNOPSIS
#include <complex.h>

double complex cacosh(double complex z);
float complex cacoshf(float complex z);
long double complex cacoshl(long double complex z);

Link with -lm.

DESCRIPTION
These functions calculate the complex arc hyperbolic cosine of z. If y = cacosh(z), then z = ccosh(y). The imaginary part of y is chosen in the interval [-pi,pi]. The real part of y is chosen nonnegative.

One has:

    cacosh(z) = 2 * clog(csqrt((z + 1) / 2) + csqrt((z - 1) / 2))

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.

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;

        if (argc != 3) {
            fprintf(stderr, "Usage: %s <real> <imag>\n", argv[0]);
            exit(EXIT_FAILURE);
        }

        z = atof(argv[1]) + atof(argv[2]) * I;

        c = cacosh(z);
        printf("cacosh() = %6.3f %6.3f*i\n", creal(c), cimag(c));

        f = 2 * clog(csqrt((z + 1)/2) + csqrt((z - 1)/2));
        printf("formula  = %6.3f %6.3f*i\n", creal(f2), cimag(f2));

        exit(EXIT_SUCCESS);
    }

SEE ALSO
acosh(3), cabs(3), ccosh(3), cimag(3), complex(7)

COLOPHON
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