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():
           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED ||
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99
       acoshf(), acoshl():
           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99

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 functions 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:

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

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).
       ┌──────────────────────────────┬───────────────┬─────────┐
       │ Interface                    │ Attribute     │ Value   │
       ├──────────────────────────────┼───────────────┼─────────┤
       │ acosh(), acoshf(), acoshl()  │ Thread safety │ MT-Safe │
       └──────────────────────────────┴───────────────┴─────────┘

CONFORMING TO

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

       The variant returning double also conforms to SVr4, 4.3BSD, C89.

SEE ALSO

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

COLOPHON

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       http://www.kernel.org/doc/man-pages/.

                                                   2015-04-19                                           ACOSH(3)