Question Number 98986 by Ar Brandon last updated on 17/Jun/20
$$\mathrm{Is}\:\mathrm{the}\:\mathrm{sequence}\:\mathrm{u}_{\mathrm{n}} =\mathrm{cos}\left(\frac{\mathrm{n}\pi}{\mathrm{20}}\right)\:\mathrm{divergent}? \\ $$
Answered by maths mind last updated on 17/Jun/20
$${u}_{\mathrm{40}{n}+\mathrm{10}} =\mathrm{0} \\ $$$${u}_{\mathrm{40}{n}} =\mathrm{1} \\ $$$$\Rightarrow{u}_{{n}} \:{has}\:{no}\:{limite} \\ $$
Commented by Ar Brandon last updated on 18/Jun/20
$$\mathrm{thanks} \\ $$