How to find sigma(summation) n from -N to N for the exp
cos2(4n+60)?
Thank you
According to a pm from vikrant, Prove It has the correct formula to be evaluated, I believe. So, what's desired is
$\displaystyle \displaystyle\sum_{n=-N}^{N}\cos(8n+120).$
I am not qualified to answer this question (other than simply asking Mathematica to spit out the answer, which it does), so someone else please continue.