那一个点落在这圆的圆周线上。

That point falls on the circumference of the circle.

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下面我们写一个函数作为例子，这个函数需要两个点，一个是圆心，一个是圆周上面的点，函数要用来计算这个圆的面积。

As an example, we'll write a function that takes two points, the center of the circle and a point on the perimeter, and computes the area of the circle.

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