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# Math.acosh()

The **`Math.acosh()`** function returns the inverse hyperbolic cosine of a number.

## Syntax

```js
Math.acosh(x)
```

### Parameters

- `x`
  - : A number greater than or equal to 1.

### Return value

The inverse hyperbolic cosine of `x`. If `x` is less than 1, returns `NaN`.

## Description

Because `acosh()` is a static method of `Math`, you always use it as `Math.acosh()`, rather than as a method of a `Math` object you created (`Math` is no constructor).
