> ## 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If you encounter incorrect, outdated, or confusing documentation on this page, submit feedback: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/tan",
  "feedback": "Description of the issue"
}
```

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

</AgentInstructions>

# tan

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

Use the `tan` function in APL to compute the tangent of an angle expressed in radians. The tangent is defined as the ratio of the sine to the cosine: `tan(x) = sin(x) / cos(x)`. The function is undefined at odd multiples of π/2, where the cosine is zero.

`tan` is useful when you work with angular data or want to convert a ratio into an angle. In observability contexts, it can be used alongside `sin` and `cos` to encode periodic signals or compute angular features for cyclic analysis.

## 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, `tan()` takes an angle in radians and returns the tangent, just like APL.

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

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

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

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

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

## Usage

### Syntax

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

### Parameters

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

### Returns

The tangent of `x`. The result is unbounded, approaching ±∞ near odd multiples of π/2.

## Example

Use `tan` to compute the tangent of an angle in radians.

**Query**

```kusto theme={null}
print result = tan(pi() / 4)
```

[Run in Playground](https://play.axiom.co/axiom-play-qf1k/query?initForm=%7B%22apl%22%3A%20%22print%20result%20%3D%20tan%28pi%28%29%20/%204%29%22%7D)

**Output**

| result |
| ------ |
| 1.0000 |

## List of related functions

* [sin](/apl/scalar-functions/mathematical-functions/sin): Returns the sine. Use `sin` and `cos` together for bounded cyclic encoding instead of `tan`, which is unbounded.
* [cos](/apl/scalar-functions/mathematical-functions/cos): Returns the cosine. It is the denominator in `tan(x) = sin(x) / cos(x)`.
* [cot](/apl/scalar-functions/mathematical-functions/cot): Returns the cotangent, the reciprocal of `tan`. Use it when you need the inverse ratio.
* [atan](/apl/scalar-functions/mathematical-functions/atan): Returns the arc tangent. Use it as the inverse of `tan`.
* [isfinite](/apl/scalar-functions/mathematical-functions/isfinite): Returns whether a value is finite. Use it to filter out `tan` overflow values near π/2 poles.