I must be missing something since I don't see a proof here. What is [imath]v_n[/imath]? And why using [imath]\cos(n\pi)[/imath] is better than using [imath](-1)^n[/imath] ?
and this series convege?
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I would apply the root test to determine the convergence of the series, but I haven't worked it out yet.and this series convege?
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