Does the series \sum^{\infty}_{n=1}sin(\frac{1}{n^{4}}) converge?

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Homework Help Overview

The discussion revolves around the convergence of the series \(\sum^{\infty}_{n=1}\sin\left(\frac{1}{n^{4}}\right)\). Participants are exploring whether the series diverges, converges conditionally, or converges absolutely.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to apply various convergence tests, noting the limit of the sequence is 0 and questioning the applicability of the integral test, root test, and ratio test. They express uncertainty about using limit comparison and seek guidance on potential approaches.

Discussion Status

Some participants suggest using limit comparison with the series \(\frac{1}{n^4}\), indicating that this could be a viable approach. There is a recognition of the challenges faced during the test, and a mix of interpretations regarding the application of different tests is evident.

Contextual Notes

The original poster mentions that this problem was part of a test and expresses doubt about receiving adequate explanations from their teacher, which may influence their understanding of the topic.

Bipolarity
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Homework Statement



Determine whether the following series diverges, converges conditionally, or converges absolutely.

\sum^{\infty}_{n=1}sin(\frac{1}{n^{4}})

Homework Equations


The Attempt at a Solution


This was on today's test, and was the only problem I wasn't able to solve. I doubt my teacher will be going over these, and in any case his explanations never satisfy me, so could someone help me with this?

According to the nth term test, the limit of the sequence is 0, since sin(x) is continuous, so the function doesn't necessarily diverge.

Integral test can't be applied because the sequence is not monotonic. Root test serves no purpose. Limit comparison might work, but with what? Ratio does not work (I think?).

How might I approach this?

BiP
 
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Hedi beat me to it down below VVV haha. I forgot that something bigger that diverges tells you nothing.
 
Last edited:
use limit comparison with 1/n^4.for large n this is a positive series.
 
hedipaldi said:
use limit comparison with 1/n^4.for large n this is a positive series.

Thanks!

But damn! I wish I thought of that in the test! Oh well.

BiP
 

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