This formula is used to calculate the area of a circle.

这个公式用于计算圆的面积。

《牛津词典》

Example: Functional index on the area of a circle

示例：对圆的面积执行函数索引

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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。

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His family said he was well-known around the area and had a big circle of friends who were "absolutely devastated" by his sudden death.

BBC: Tribute to Cumbria crash driver Billy Parker

France is a country with many obvious problems, but in the area of food, it has excelled in creating a virtuous circle of people who love making food and people who appreciate food that is well made.

FORBES: Radical Management In France: The Quest For Heavenly Bread