Question Number 109213 by mathmax by abdo last updated on 22/Aug/20
$$\mathrm{find}\:\mathrm{nature}\:\mathrm{of}\:\sum_{\mathrm{n}=\mathrm{0}} ^{\infty} \:\frac{\left(−\mathrm{1}\right)^{\left[\mathrm{x}\right]} }{\mathrm{2}+\mathrm{cos}\left(\mathrm{n}\left[\mathrm{x}\right]\right)}\:\:\mathrm{with}\:\left[..\right]\:\mathrm{mean}\:\mathrm{floor} \\ $$