ACOSH(3M) | Mathematical Library Functions | ACOSH(3M) |

acosh, acoshf, acoshl - inverse hyperbolic cosine functions

c99 [flag... ]file...-lm[library... ] #include <math.h>doubleacosh(doublex);

floatacoshf(floatx);

long doubleacoshl(long doublex);

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

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.

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.

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**.

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE | ATTRIBUTE VALUE |

Interface Stability | Standard |

MT-Level | MT-Safe |

math.h(3HEAD), cosh(3M), feclearexcept(3M), fetestexcept(3M), matherr(3M), attributes(7), standards(7)

July 12, 2006 | SunOS 5.11 |