bottom face

基本解释

Let's call that R. And, it lives between the top face and the bottom face.
称为R，该图形在顶面和底面之间。
So, it's something that has a bottom face, and a top face, and then some vertical sides.
它有一个底面和一个顶面，还有垂直的侧面。
So, remember, when we set up the divergence theorem, we need the normal vectors to point out of our region, which means that on the top surface, n But, on the bottom face, we want n pointing down.
当我们建立散度定理时，我们要使法向量指向区域外，即在上表面时，要指向上方。，we，want，n，pointing，up。,但是，在下表面，要使n指向下面。

My only complaint would be the clear key, which is centered at the bottom of the face.
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