> ## Documentation Index
> Fetch the complete documentation index at: https://axiom.co/docs/llms.txt
> Use this file to discover all available pages before exploring further.

<AgentInstructions>

## Submitting Feedback

If you encounter incorrect, outdated, or confusing documentation on this page, submit feedback:

POST https://axiom.co/docs/feedback

```json
{
  "path": "/apl/scalar-functions/mathematical-functions/cos",
  "feedback": "Description of the issue"
}
```

Only submit feedback when you have something specific and actionable to report.

</AgentInstructions>

# cos

> This page explains how to use the cos function in APL.

Use the `cos` function in APL to compute the cosine of an angle expressed in radians. The function accepts any real number and returns a value in the range \[-1, 1].

`cos` is useful in observability and log analysis when you need to encode time-of-day or other cyclic patterns as a continuous numeric feature. For example, you can combine `cos` and `sin` to represent hour-of-day as a pair of cyclic coordinates, which preserves the circular distance between hours for anomaly detection or grouping.

## For users of other query languages

If you come from other query languages, this section explains how to adjust your existing queries to achieve the same results in APL.

<AccordionGroup>
  <Accordion title="Splunk SPL users">
    In Splunk SPL, `cos()` is available in the `eval` command with the same behavior: it takes an angle in radians and returns the cosine.

    <CodeGroup>
      ```sql Splunk example theme={null}
      | eval cos_val = cos(angle_rad)
      ```

      ```kusto APL equivalent theme={null}
      ['sample-http-logs']
      | extend cos_val = cos(angle_rad)
      ```
    </CodeGroup>
  </Accordion>

  <Accordion title="ANSI SQL users">
    In ANSI SQL, `COS()` is a standard mathematical function with identical semantics.

    <CodeGroup>
      ```sql SQL example theme={null}
      SELECT COS(angle_rad) AS cos_val FROM logs
      ```

      ```kusto APL equivalent theme={null}
      ['sample-http-logs']
      | extend cos_val = cos(angle_rad)
      ```
    </CodeGroup>
  </Accordion>
</AccordionGroup>

## Usage

### Syntax

```kusto theme={null}
cos(x)
```

### Parameters

| Name | Type | Required | Description           |
| ---- | ---- | -------- | --------------------- |
| `x`  | real | Yes      | The angle in radians. |

### Returns

The cosine of `x`, a real number in the range \[-1, 1].

## Example

Use `cos` to compute the cosine of an angle in radians.

**Query**

```kusto theme={null}
print result = cos(pi())
```

[Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%20%22print%20result%20%3D%20cos%28pi%28%29%29%22%7D)

**Output**

| result |
| ------ |
| -1     |

## List of related functions

* [sin](/apl/scalar-functions/mathematical-functions/sin): Returns the sine. Use `sin` and `cos` together to produce a two-dimensional cyclic encoding of angles.
* [tan](/apl/scalar-functions/mathematical-functions/tan): Returns the tangent. Use it when you need the ratio of sine to cosine.
* [acos](/apl/scalar-functions/mathematical-functions/acos): Returns the arc cosine. Use it as the inverse of `cos`.
* [pi](/apl/scalar-functions/mathematical-functions/pi): Returns the constant π. Use it to compute angle values in radians.
* [radians](/apl/scalar-functions/mathematical-functions/radians): Converts degrees to radians. Use it to prepare angle inputs before calling `cos`.