Sun Microsystems, Inc. gratefully acknowledges The Open Group for
permission to reproduce portions of its copyrighted documentation.
Original documentation from The Open Group can be obtained online at
http://www.opengroup.org/bookstore/.

The Institute of Electrical and Electronics Engineers and The Open
Group, have given us permission to reprint portions of their
documentation.

In the following statement, the phrase ``this text'' refers to portions
of the system documentation.

Portions of this text are reprinted and reproduced in electronic form
in the SunOS Reference Manual, from IEEE Std 1003.1, 2004 Edition,
Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6,
Copyright (C) 2001-2004 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy
between these versions and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html.

This notice shall appear on any product containing this material.

The Berkeley software License Agreement specifies the terms and conditions
for redistribution.


Copyright (c) 1983 Regents of the University of California.
All rights reserved.
Copyright (c) 1992, X/Open Company Limited. All Rights Reserved.
Copyright (c) 2001, The IEEE and The Open Group. All Rights Reserved.
Portions Copyright (c) 2002, Sun Microsystems, Inc. All Rights Reserved.

ACOSH 3M "Jul 12, 2006" "SunOS 5.11" "Mathematical Library Functions"
NAME
acosh, acoshf, acoshl - inverse hyperbolic cosine functions
SYNOPSIS

c99 [ flag... ] file... -lm [ library... ]
#include <math.h>

double acosh(double x);

float acoshf(float x);

long double acoshl(long double x);
DESCRIPTION

These functions compute the inverse hyperbolic cosine of their argument x.

RETURN VALUES

Upon successful completion, these functions return the inverse hyperbolic cosine of their argument.

For finite values of x < 1, a domain error occurs and NaN is returned.

If x is NaN, NaN is returned.

If x is +1, +0 is returned.

If x is +Inf, +Inf is returned.

If x is -Inf, a domain error occurs and NaN is returned.

For exceptional cases, matherr(3M) tabulates the values to be returned by acosh() as specified by SVID3 and XPG3.

ERRORS

These functions will fail if:

Domain Error

The x argument is finite and less than 1.0, or is -Inf. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the invalid floating-point exception is raised. The acosh() function sets errno to EDOM if x is less than 1.0.

USAGE

An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception has been raised. An application should either examine the return value or check the floating point exception flags to detect exceptions.

An application can also set errno to 0 before calling acosh(). On return, if errno is non-zero, an error has occurred. The acoshf() and acoshl() functions do not set errno.

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE ATTRIBUTE VALUE
Interface Stability Standard
MT-Level MT-Safe
SEE ALSO

cosh(3M), feclearexcept(3M), fetestexcept(3M), math.h(3HEAD), matherr(3M), attributes(5), standards(5)