Well, if I take the vector field that was in the problem set, and if I do things, say that I look at the unit circle.
如果找一个这个问题中的向量场，然后我们要做的是，假设这个单位圆。
If you look at the vector from behind, you see a cross.
如果矢量背对你，你看到的是一个叉。
Ok, so just to reinforce my warning that not every field is a gradient field, let's look again at our favorite vector field from yesterday.
好的，为了强调，不是所有场都是梯度场，我们再来看看昨天那个向量场。
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