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Prove that sum(k=1)^(n-1)(n-k)cos(2kpi)...

Prove that `sum_(k=1)^(n-1)(n-k)cos(2kpi)/n=-n/2,w h e r engeq3i sa nin t ege r`

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A DAS GUPTA-Integrated Tests-Exercise
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  9. Prove that sum(k=1)^(n-1)(n-k)cos(2kpi)/n=-n/2,w h e r engeq3i sa nin...

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