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Why do equations typically have variable names like x and y?

In computer programming, we value meaningful names for variables. For example, if I were trying to calculate a square root, I would call the value I was trying to determine square_root, not x. This makes my code easier to understand.

Is this common in math and I just don't realize it?

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The use of $x$ roots back to the arabs. The $y$ is just a natural continuation using our alphabet. – Pedro Tamaroff Mar 21 '13 at 14:31
Viète used vowels to denote unknowns; it was Descartes that started using $x$ and $y$. – egreg Mar 21 '13 at 14:45
Isn't this a duplicate question: why mathematics doesn't use descriptive names for variables? Of course Einstein should have written Energy = Mass x Speed_Of_Light^2 – GEdgar Mar 21 '13 at 14:53

Well because $x$ and $y$ are short, and mathematicans are lazy. It would be much more work to write every time the name, which is really annoying if you do a lot of calculation.

And math ist very abstract, so meaningful names can't be found everytime, and it is often so that we generalize something, so we just interprete $x$ as something different, and maybe in the new interpretation the old meaningfull name would be totally senseless.

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