It's the same vector So, a lot of vectors we'll draw starting at the origin but we don't have to.

它们是同一个向量，通常我们都选原点作为向量的起点，但是我们不一定要这么做。

youdao

And, of course, I am not going to try to draw all these vectors in there.

当然，我无法画出所有的向量。

youdao

If the two level curves are tangent to each other that means they have the same tangent line. That means that the normal vectors should be parallel. Let me maybe draw a picture here.

如果两个等高线相切，说明它们的切线相同，也就是说他们的法向量应该平行，我再在这里画个图。

youdao