Daily DAX : Day 267 PI

 The **PI** function in Power BI DAX (Data Analysis Expressions) returns the mathematical constant π (pi), approximately equal to 3.14159. It takes no arguments and is used in calculations involving circular or trigonometric computations.

### Syntax

```dax

PI()

```

### Return Value

A constant value of π (3.14159265358979).

### Use Case

The PI function is commonly used in scenarios involving geometry, trigonometry, or calculations requiring the constant π, such as:

- **Calculating the area or circumference of a circle** (e.g., Area = π * radius², Circumference = 2 * π * radius).

- **Trigonometric calculations** involving angles (e.g., using SIN, COS, or TAN functions in DAX).

- **Engineering or financial models** where circular or periodic phenomena are analyzed.

### Example

Suppose you have a table with a column `Radius` containing the radius of circles, and you want to calculate the area.

1. Create a new calculated column in Power BI:

   ```dax

   CircleArea = PI() * [Radius] * [Radius]

   ```

   This multiplies π by the square of the radius to compute the area.

2. Alternatively, for circumference:

   ```dax

   Circumference = 2 * PI() * [Radius]

   ```

### Practical Scenario

In a manufacturing dataset, you might use the PI function to calculate the material needed for circular components (e.g., pipes, wheels). For example, a measure to calculate the total area of multiple circular parts could be:

```dax

TotalArea = SUMX(TableName, PI() * [Radius] * [Radius])

```

### Notes

- The PI function is simple and doesn’t require parameters, making it straightforward for geometric calculations.

- Combine it with other DAX functions like `SIN`, `COS`, or `POWER` for more complex trigonometric or engineering calculations.

- Ensure the input values (e.g., radius) are in the correct units for accurate results.