Does the series Ʃ[k=1,inf] tan(k)/(k^2+1) converge or diverge?

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Homework Help Overview

The discussion revolves around determining the convergence or divergence of the series Ʃ[k=1,inf] tan(k)/(k^2+1). The original poster expresses uncertainty regarding how to approach series involving tangent functions, particularly in relation to their behavior at specific points.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • The original poster attempts to reason through the properties of the tangent function and its implications for the series. They question whether the undefined nature of tangent at certain points affects convergence. Another participant mentions the integral test as a potential method but does not elaborate further.

Discussion Status

The discussion is ongoing, with participants exploring different aspects of the problem. Some guidance has been suggested regarding the integral test, but no consensus has been reached on the convergence of the series. The original poster's concerns about the behavior of the tangent function and its impact on the series are acknowledged.

Contextual Notes

The original poster raises questions about the implications of undefined points in functions and the possibility of multiple intervals of convergence, indicating a broader exploration of series convergence concepts.

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Homework Statement



Determine if the following series converges or diverges.

Ʃ[k=1,inf] tan(k)/(k^2+1)

Homework Equations





The Attempt at a Solution



I have no idea how to solve this problem. Now that I think of it, I have never solved a single question about series were I'm asked about convergence or divergence of a series with tangent or cotangent as part of the series. Tangent and cotangent are not defined at multiples of pi/2 excluding multiples of pi, but the series is from k to infinity were k is the set of integers and so the numerator all by itself would never go to positive or negative infinity at any k. Yet I can't seem to come up with a solution to this problem.

Also just a quick question. If I'm given a particular series in which I know the function which it represents, if the function is undefined at some given points, like for example 1/(2-x) or something of the sort, could I automatically conclude that the series doesn't converge at positive 2 sense the function doesn't?

Also I have never seen a problem were the interval of convergence included two intervals like [-10,5)(5,22] or something of the sort just [-10,5) if that makes any sense at all. Is it possible to have series were there are two intervals of convergence instead of just one?

Thank you for any help
 
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I posted a message about this series in the Homework Helpers' section. Maybe somebody there will have a good idea. The integral test seems like a way to go, but I haven't carried it all the way through.
 
I believe this series diverges.

A condition for a series to converge is that it needs to be possible for any epsilon > 0, that there is an N'th term such that all subsequent terms have an absolute value less than epsilon.

tan(k) can get arbitrarily large as k comes arbitrarily close to pi/2 + m pi for some m.
However large you want it to be, you can get it for some k.
So you can make always find a term larger than epsilon.

However, I'm afraid my argument isn't completely rigorous yet.
 

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