(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

I saw the following equation in my (Zwiebach page 83).

[tex]2 ds \delta (ds) = \delta (ds) ^2 [/tex]

where delta is the variation from variational calculus and ds is the Lorentz invariant spacetime distance.

It seems like they took a derivative from the right to the left but I am really not sure why you can do that because I thought delta was just a very small variation function.

2. Relevant equations

3. The attempt at a solution

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# Homework Help: String theory question

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