This time I used the Pen Tool (P) , because it has the possibility to make nice curves.

这一次我用钢笔工具（规划）， 因为它有可能使好曲线。

youdao

And the bubble line. Sometimes, instead of having a nice separation between the bubble and the dew line, there's a special point which for some reason those two curves meet. Non-ideality.

这是汽化线，有时汽化和液化曲线没有完全分开，因为某些原因，这两条线会在某个点相交，非理想情况。

youdao

OK, so let me show you a nice example of why we might want to use vectors to study parametric curves because, after all, a lot of what's here you can just do in coordinates.

我来举个例子，解释为什么我们用向量来学习参数曲线，毕竟我们学了这么多的都只能在坐标上完成。

youdao

I should be able to do nice bell-shaped curves, but it's harder than it looks standing up here; so that's your bell-shaped curve.

我还是挺擅长画钟型曲线的,但站着画真的不太容易,这就是钟型曲线

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