Question Number 92768 by mathmax by abdo last updated on 09/May/20
$${calculate}\:{A}_{{n}} =\:\sum_{{k}=\mathrm{0}} ^{{n}} \:{C}_{{n}} ^{{k}} \:{cos}^{\mathrm{3}} \left({kx}\right)\:\:{and}\:\sum_{{k}=\mathrm{0}} ^{{n}} \:{C}_{{n}} ^{{k}} \:{sin}^{\mathrm{3}} \left({kx}\right) \\ $$