## TAU

TAU function in ES|QL returns the ratio of a circle’s circumference to its radius.

### Examples

Here are a couple of examples of how to use the TAU function in ES|QL:

```esql
ROW TAU()
```

In this example, the TAU function is used to return the ratio of a circle’s circumference to its radius.

```esql
FROM my-index
| EVAL tau_ratio = TAU()
```

In this example, the TAU function is used within an EVAL function to create a new column `tau_ratio` in the result set, which contains the ratio of a circle’s circumference to its radius.