Question Number 137696 by Mathspace last updated on 05/Apr/21
$${let}\:{U}_{{n}} =\int_{\mathrm{0}} ^{\infty} \:\frac{{cos}\left({nsinx}\right)−{sin}\left({ncosx}\right)}{\left({x}^{\mathrm{2}} \:+\mathrm{3}\right)^{\mathrm{2}} }{dx} \\ $$$${determine}\:{lim}_{{n}\rightarrow+\infty} {U}_{{n}} \\ $$$${and}\:{lim}_{{n}\rightarrow+\infty} {e}^{−{n}^{\mathrm{2}} } \:{U}_{{n}} \\ $$