What he did was coined this. But he found that by taking the reciprocal of the wavelengths, you have four numbers, he took the reciprocals of those wavelengths and found that they fit a numerical sequence.

这些都是由他所做的一切得来的,但是他发现通过取波长的倒数，你有四个数字，他取了这些波长的倒数,发现它们构成了一个数列。

麻省理工公开课 - 固态化学导论课程节选

So, what we have found out so far, I'm purposely going from x to y because I want you to know that the unknown variable can be called an x or can be called a y.

到目前为止,我们有这些结论,我特地把x换成y,因为我想让你们明白,未知变量既可以写成x,也可以写成y

耶鲁公开课 - 基础物理课程节选