# ACOSH

## Purpose:

Calculates the inverse hyperbolic cosine of any expression.

## Syntax:

ACOSH(val)

 val - A scalar, series or table.

## Returns:

A scalar, series, or table.

## Example:

acosh(1..pi/100..pi);gridhv;griddot

displays the hyperbolic inverse cosine from 1 to π.

## Example:

acosh(2)

returns 1.3169579.

## Example:

acosh(-2..0.1..2)

returns a 41 point complex series.

## Remarks:

The inverse hyperbolic cosine is defined as:

for all complex z. The function is multi-valued and this definition places the branch cut in the complex plane at [-∞, 1].

For real x, where x < 0, acosh(x) returns a complex result.

SETDEGREE and SETRADIAN have no effect on this function because it always operates in radians.