ACOSH(3)                  (2017-09-15)                   ACOSH(3)

     NAME
          acosh, acoshf, acoshl - inverse hyperbolic cosine function

     SYNOPSIS
          #include <math.h>

          double acosh(double x);
          float acoshf(float x);
          long double acoshl(long double x);

          Link with -lm.

     Feature Test Macro Requirements for glibc (see
     feature_test_macros(7)):

          acosh():
              _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
                  || _XOPEN_SOURCE >= 500
                  || /* Since glibc 2.19: */ _DEFAULT_SOURCE
                  || /* Glibc versions <= 2.19: */ _BSD_SOURCE ||
              _SVID_SOURCE
          acoshf(), acoshl():
              _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
                  || /* Since glibc 2.19: */ _DEFAULT_SOURCE
                  || /* Glibc versions <= 2.19: */ _BSD_SOURCE ||
              _SVID_SOURCE

     DESCRIPTION
          These functions calculate the inverse hyperbolic  cosine  of
          x; that is the value whose hyperbolic cosine is x.

     RETURN VALUE
          On success, these functions return  the  inverse  hyperbolic
          cosine of x.

          If x is a NaN, a NaN is returned.

          If x is +1, +0 is returned.

          If x is positive infinity, positive infinity is returned.

          If x is less than 1, a domain error occurs,  and  the  func-
          tions return a NaN.

     ERRORS
          See  math_error(7)  for  information  on  how  to  determine
          whether an error has occurred when calling these functions.

          The following errors can occur:

     Page 1                       Plan 9             (printed 5/20/22)

     ACOSH(3)                  (2017-09-15)                   ACOSH(3)

          Domain error: x is less than 1
               errno is set to EDOM.  An invalid floating-point excep-
               tion (FE_INVALID) is raised.

     ATTRIBUTES
          For an explanation of the terms used in  this  section,  see
          attributes(7).     allbox;    lbw28    lb    lb   l   l   l.
          Interface Attribute Value  T{  acosh(),  acoshf(),  acoshl()
          T}   Thread safety  MT-Safe

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

          The variant returning double also conforms to SVr4, 4.3BSD.

     SEE ALSO
          asinh(3), atanh(3), cacosh(3), cosh(3), sinh(3), tanh(3)

     COLOPHON
          This page is part of release 5.10  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/.

     Page 2                       Plan 9             (printed 5/20/22)