Representing a Sum of a Series as a Function

1. Dec 12, 2009

color_me

1. The problem statement, all variables and given/known data
http://i29.photobucket.com/albums/c252/lostsun/problem_statement.jpg" [Broken]
Find a function to represent the series and then find f(?) that will represent its sum.

2. Relevant equations

3. The attempt at a solution
I kind of understand how to come up with a function, but then how do I know what value to plug into the function to get the sum? Thank you for any help!

Last edited by a moderator: May 4, 2017
2. Dec 12, 2009

zcd

it should help to know that $$\tan{x}=\sum_{n=0}^{\infty}(-1)^{n}\frac{x^{2n+1}}{2n+1}$$