Hi! I am attempting to derive the wave equation (classical physics) and having trouble understanding this step. I have not taken differential equations, but I do have a highschool understanding of derivatives and integrals --- wondering if anyone can explain what's going on here. This is the video it's from: https://www.youtube.com/watch?v=CifQ-BhBQSA. Timestamp is 5:20.
In this video, I introduce the Wave Equation. I carry out a derivation of the Wave Equation for a 1-D string by using force balances and applying a small amplitude approximation. I also give some of the intuition of the wave equation to give a better idea of what it means, kind of like what I did with the Heat Equation here: https://www.youtube....