Sum of Series using Cosine Function | Homework Equations and Solution Attempt

[rcmango]

Homework Statement

heres the equation: http://img255.imageshack.us/img255/1669/untitledfa5.jpg

Homework Equations

i think we use cos(x)

The Attempt at a Solution

i know that cos(x) = cos(pi)

so the limit is -1?

whats the sum, I'm a bit confused.
must be in simplest form
what must i show. help.

 

[Dick]

I don't think you can express the sum much more simply than -1. The 'limit' you are talking about is the 'sum', right?

 

[arildno]

What you must show is that the infinite series representation of $\cos(\pi)$ is identical to the infinite series given in the exercise.

 

[rcmango]

excellent, okay you its simple it is only -1. I just wasn't sure what they wanted to see. thanks