Question Number 28612 by abdo imad last updated on 27/Jan/18
$${let}\:{give}\:\:{u}_{{n}\:} =\:\sum_{{k}=\mathrm{1}} ^{{n}} \:\:\frac{{sin}\left({k}\alpha\right)}{{n}+{k}}\:{and}\:\:\alpha\in{R} \\ $$$${find}\:{lim}\:_{{n}\rightarrow+\infty} {u}_{{n}} \:\:. \\ $$