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

Click For Summary
SUMMARY

The series Ʃ[k=1,inf] tan(k)/(k^2+1) diverges due to the behavior of the tangent function. As k approaches values of the form π/2 + mπ, where m is an integer, tan(k) becomes unbounded, leading to terms in the series that do not approach zero. The integral test was suggested as a potential method for analysis, but the conclusion remains that the series diverges based on the properties of the tangent function.

PREREQUISITES
  • Understanding of series convergence and divergence criteria
  • Familiarity with the properties of the tangent function
  • Knowledge of the integral test for convergence
  • Basic concepts of limits and epsilon-delta definitions
NEXT STEPS
  • Study the integral test for series convergence in detail
  • Explore the behavior of the tangent function near its asymptotes
  • Investigate other convergence tests such as the comparison test
  • Learn about series with piecewise-defined functions and their convergence properties
USEFUL FOR

Students studying calculus, particularly those focusing on series and convergence tests, as well as educators seeking to clarify concepts related to series divergence.

GreenPrint
Messages
1,186
Reaction score
0

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
 
Physics news on Phys.org
=( ah man
 
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.
 

Similar threads

  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
1K
  • · Replies 4 ·
Replies
4
Views
20K
  • · Replies 8 ·
Replies
8
Views
5K
  • · Replies 22 ·
Replies
22
Views
3K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K