Question regarding the derivation of the wave equation

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SUMMARY

The discussion focuses on the derivation of the wave equation, specifically addressing a transformation involving limits and the square root function. The author questions how the expression √(Δx² + Δu²) can be simplified to √(1 + (du/dx)²) as Δx approaches 0. The solution hinges on the limit property of the n-th root, which states that the limit of the n-th root of a function equals the n-th root of the limit of that function, applicable here with n set to 2.

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Homework Statement


There's a derivation here that I'm looking at, and I've hit a snag. At (1) about 15 lines down the page, the author divides by Δx and takes the limit as Δx goes to 0. I understand what he did on the right side of the equation, but on the left side of the equation, by what means is he able to transform √(Δx2 + Δu2) into √(1 + (du/dx)2)? I'm kind of lost there.
[/B]
http://www.math.ubc.ca/~feldman/m256/wave.pdf

Homework Equations

The Attempt at a Solution

 
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It uses the following property of limits:

The limit of the n-th root of function f(x) exists and is equal to the n-th root of the limit of f(x), if the latter exists.

Here n is 2.

The property is often taught in teaching limits, and is easy to prove using epsilon-delta arguments.
 

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