## Purpose

## Return value

## Syntax

`=ACOSH(number)`

*number*- The inverse hyperbolic cosine of a number.

## How to use

The Excel ACOSH function returns the inverse hyperbolic cosine of a number. Given the input 2.0, the function returns the value 1.316957897.

```
=ACOSH(2) // returns 1.316957897
```

### Explanation

Given the *x*-component of a point that lies on the right branch of the unit hyperbola given by the equation x² - y² = 1, the ACOSH function returns the hyperbolic angle formed by the point.

```
=ACOSH(1.543080634) // returns 1
```

In other words, the ACOSH function returns twice the area of the sector formed between the origin, the x-axis, and the point on the hyperbola.

### Notes

- The function throws a #NUM! Error when given a number less than 1.

*Images courtesy of wumbo.net.*