在曲面上做一些网格，你会看到一个网上的每一小块儿，都是小的平行四边形，我们要弄清楚它的面积和法向量是什么。

You will get some sort of mesh grid on your surface and you will look at a little parallelogram that is an elementary piece of that mesh and figure out what is its area and normal vector.

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这面积，约等于平行四边形的一半，我能用向量表示它。

So, the area is approximately equal to one half of the area of a parallelogram that I could form from these vectors.

youdao