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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