Question Number 36746 by prof Abdo imad last updated on 05/Jun/18
$${solve}\:{the}\:{d}.{e}.\:{y}^{''} \left({t}\right)\:+{y}\left({t}\right)=\sum_{{n}=\mathrm{0}} ^{{N}} \:{a}_{{n}} {cos}\left({nt}\right) \\ $$
solve-the-d-e-y-t-y-t-n-0-N-a-n-cos-nt-