- #1

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## Homework Statement

the answer that i get is different with the answer provided , is my answer wrong ? i got ( cos(2n -1) / 2n-1 )instead of ( cos(n+1) / n+1 )

## Homework Equations

## The Attempt at a Solution

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- Thread starter foo9008
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- #1

- 678

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the answer that i get is different with the answer provided , is my answer wrong ? i got ( cos(2n -1) / 2n-1 )instead of ( cos(n+1) / n+1 )

[/B]

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- #2

vela

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www.desmos.com is useful if you don't have access to plotting software.

- #3

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I am not interested in the graph, I just wanna know the final answer....

www.desmos.com is useful if you don't have access to plotting software.

- #4

Samy_A

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I actually followed vela's good advice, and the result is telling ...I am not interested in the graph, I just wanna know the final answer....

Another test you could try: what happens with the given solution (answer b) when x=π?

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- #5

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Cos(n +1 ) pi= (-1)^n.... What can we conclude from that??I actually followed vela's good advice, and the result is telling ...

Another test you could try: what happens with the given solution (answer b) when x=π?

- #6

Samy_A

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No, that is not correct.Cos(n +1 ) pi= (-1)^n.... What can we conclude from that??

##\cos 2 \pi = \cos (1+1) \pi \neq {(-1)}^1##

Once you have the correct values, plug them in into the Fourier series of answer (b).

- #7

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It's (-1) ^ (n +1)No, that is not correct.

##\cos 2 \pi = \cos (1+1) \pi \neq {(-1)}^1##

Once you have the correct values, plug them in into the Fourier series of answer (b).

- #8

Samy_A

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Correct.It's (-1) ^ (n +1)

So what is the Fourier series of answer (b) for x=π? Does it converge? If so, to what value?

And don't forget about vela's advice: it takes 2 minutes, and yields very interesting information.

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