This formula is used to calculate the area of a circle.
这个公式用于计算圆的面积。
Example: Functional index on the area of a circle
示例：对圆的面积执行函数索引
This example shows how to create a functional index on the area of a circle.
本示例展示如何对圆的面积创建函数索引。
Next, create an SPL function that returns the area of a circle given its radius.
接着，创建一个spl函数，它将返回给定半径的圆的面积。
Create a functional index on the area of the circle.
对这个圆形区域创建一个函数索引。
Well, it's just the area of a unit circle.
这就等于一个单位圆的面积。
The radius of a circle is 4cm, how many square centimeters is its area?
一个圆的半径是4厘米，它的面积是多少平方厘米？
The radius of a circle is 4cm, how many square centimeters is its area?
一个圆的半径是4厘米，它的面积是多少平方厘米？
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