At a coexistence line, then the number of phases equals to two.

在共存曲线上，一共有两个相。

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The sentence contains two ideas and treats then as equals.

这个句子包含着两层意思，并对这两层意思作了同等的处理。

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And if that is the energy to go from n equals one n=2 this is the amount of energy that has to be left as kinetic energy of the electron.

如果这个能量是从n=1到,然后，to，n，equals，two，then,这些能量,会作为电子的动能,被消耗掉。

麻省理工公开课 - 固态化学导论课程节选

And then, if we go to n equals two, what happens?

然后，如果我们让n等于2，会是什么情况？

麻省理工公开课 - 固态化学导论课程节选