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
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				  2015-04-19			     CACOSH(3)