# Math.acos method

The `Math.acos` method returns the arccosine (or inverse cosine) of a number. The method parameter must be between `-1` to `1`, otherwise it will return `NaN`.

## Syntax

`Math.acos(number);`

## Example

Let's output the arccosine of the number `0.34`:

`console.log(Math.acos(0.37));`

The code execution result:

`1.191787306098946`

## Example

Let's output the arccosine of the number `1`:

`console.log(Math.acos(1));`

The code execution result:

`0`

## Example

The following example will output `NaN` because the parameter is greater than `1`:

`console.log(Math.acos(3));`

The code execution result:

`NaN`

## See also

- the `Math.cos` method
  that returns the cosine of a number
- the `Math.sin` method
  that returns the sine of a number
- the `Math.tan` method
  that returns the tangent of a number
- the `Math.asin` method
  that returns the arcsine of a number
- the `Math.atan` method
  that returns the arctangent of a number

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