Question Number 30507 by abdo imad last updated on 22/Feb/18
$${find}\:\int_{−\pi} ^{\pi} \:\:\frac{{dx}}{\mathrm{2}+{cosx}} \\ $$$$\left.\mathrm{2}\right)\:{if}\:\:\frac{\mathrm{1}}{\mathrm{2}+{cosx}}=\:\frac{{a}_{\mathrm{0}} }{\mathrm{2}}\:+\sum_{{n}\geqslant\mathrm{1}} {a}_{{n}} \:{cos}\left({nx}\right)\:\:{find}\:{a}_{\mathrm{0}} \:{and}\:{a}_{{n}} \:. \\ $$