Question Number 64886 by mathmax by abdo last updated on 22/Jul/19
$${let}\:{f}\left({x}\right)\:={cos}\left(\frac{\mathrm{1}}{{x}}\right)\:\:\: \\ $$$$\left.\mathrm{1}\right)\:{calculate}\:{f}^{\left({n}\right)} \left({x}\right) \\ $$$$\left.\mathrm{2}\right)\:{developp}\:{f}\:{at}\:{integr}\:{serie}\:{at}\:{x}_{\mathrm{0}} =\frac{\mathrm{3}}{\pi} \\ $$