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

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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.
 
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I don't think you can express the sum much more simply than -1. The 'limit' you are talking about is the 'sum', right?
 
What you must show is that the infinite series representation of \cos(\pi) is identical to the infinite series given in the exercise.
 
excellent, okay you its simple it is only -1. I just wasn't sure what they wanted to see. thanks
 

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