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 CACOSH(3) Linux Programmer's Manual 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 cacosh (), cacoshf (), cacoshl () 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;
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¶

This page is part of release 4.10 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
 2015-04-19