Math Help - Need help with a serie

Supp guys...I've got a serie I don't know how to find its limit, nor the sum!
If you could help me I would appreciate!
Here it is:

Originally Posted by javax

Supp guys...I've got a serie I don't know how to find its limit, nor the sum!
If you could help me I would appreciate!
Here it is:

As with all series, you should start by asking yourself approximately how large is the n'th term of the series. In this case, for large values of n, is approximately . Then (from the power series expansion of cos). So the series diverges, by comparison with .