ACOSH, ASINH, ATANH

ACOSH - Returns the inverse hyperbolic cosine of a number.
ASINH - Returns the inverse hyperbolic sine of a number.
ATANH - Returns the inverse hyperbolic tangent of a number.

Syntax:

ACOSH(number)
ASINH(number)
ATANH(number)

number represent the cosh, sinh, or tanh of a number.

The number you are taking the inverse hyperbolic cosine of must be greater than or equal to 1.
The number you are taking the inverse hyperbolic tangent of must be greater than -1 and less than 1.

Here is a link explaining the hyperbolic functions.
http://en.wikipedia.org/wiki/Hyperbolic_function

Examples:

=ACOSH(5) will return 2.29243167
=ASINH(-2.2) will return -1.52966050
=ACOSH(.35) will return .36544375


Screen Shot of ACOSH():