Question Number 26054 by abdo imad last updated on 18/Dec/17
$$\left.{if}\:\:\left(\mathrm{1}+{cos}\left({x}\right)\right)^{−\mathrm{1}} \:=\:{a}_{\mathrm{0}} /_{\mathrm{2}} \:\:+\sum_{{n}=\mathrm{1}} ^{{n}=\propto} \:{a}_{{n}} \:{cos}\left({nx}\right)\right) \\ $$$${find}\:{a}_{\mathrm{0}} \:{and}\:\:{a}_{{n}} ...{you}\:{can}\:{use}\:{fourier} \\ $$$${series}. \\ $$$$ \\ $$