Author Topic: Exam Practice: Prob 69-72  (Read 277 times)

Rhamel

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Exam Practice: Prob 69-72
« on: April 09, 2019, 05:30:05 PM »
When we are asked to "find the Euler-Lagrange of [some functional T[v]]" are we supposed to :
a) differentiate T[v+$\epsilon$ w] w.r.t to w and evaluate at $\epsilon = 0$ to get the EL, or
b) just plug the Lagrangian into

$$\frac{\partial}{\partial x_j} \frac{\partial \mathcal{L}}{\partial v_{x_j}} =  \frac{\partial \mathcal{L}}{\partial v}$$
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Victor Ivrii

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Re: Exam Practice: Prob 69-72
« Reply #1 on: April 09, 2019, 08:08:35 PM »
You understand, that in the left there is summation with respect to $j$?

Rhamel

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Re: Exam Practice: Prob 69-72
« Reply #2 on: April 09, 2019, 10:09:58 PM »
yes
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