Question Number 28994 by abdo imad last updated on 02/Feb/18
$${find}\:\:{A}_{{n}} =\:\:\int_{−\infty} ^{+\infty} \:\:\:\:\:\frac{{dx}}{\left(\mathrm{1}+{x}^{\mathrm{2}} \right)^{{n}} }\:\:{with}\:{n}\:{from}\:{N}\:{and}\:{n}\geqslant\mathrm{1}. \\ $$