- #1

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[tex]

\frac{\delta}{\delta \theta}(\dot{\theta} cos\theta)

[/tex]

- Thread starter Ultimâ
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- #1

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[tex]

\frac{\delta}{\delta \theta}(\dot{\theta} cos\theta)

[/tex]

- #2

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I would say product rule looks good.

- #3

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Thanks for the input, will give it a go

- #4

HallsofIvy

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tiny-tim

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Hi Ultimâ!

[tex]

\frac{\delta}{\delta \theta}(\dot{\theta} cos\theta)

[/tex]

If this is calculus of variations, doesn't [tex]\frac{\delta}{\delta \theta}[/tex] mean that you assume that [tex]\dot{\theta}[/tex] is independent of [tex]\theta[/tex], so that:

[tex]\frac{\delta}{\delta \theta}(\dot{\theta} cos\theta)\,=\,-\dot{\theta} sin\theta[/tex] ?

- #6

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I've just posted the full problem here:

https://www.physicsforums.com/showthread.php?p=1731700#post1731700

(I know cross posting is frowned upon, but I was trying split the problem down into simpler components)

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