## Area of a Circle

Given the radius of a circle, `r`

, calculate and return the area of the circle.

The formula to calculate the area of a circle is

\(\LARGE area = \pi \times radius^{2}\)

Hint: Use `Math.PI`

as \(\Large \pi\) instead of 3.14.

```
circleArea( 5 ) => 78.539816
circleArea( 3 ) => 28.274333
circleArea( 7 ) => 153.93804
```