Question Number 89029 by Jidda28 last updated on 14/Apr/20
Commented by MJS last updated on 14/Apr/20
$${t}=\sqrt[{\mathrm{4}}]{\mathrm{tan}\:{x}}\:\mathrm{or}\:{t}=\frac{\mathrm{1}}{\:\sqrt[{\mathrm{4}}]{\mathrm{tan}\:{x}}}\:\mathrm{and}\:\mathrm{then}\:\mathrm{decompose} \\ $$$$\frac{{f}\left({t}\right)}{{t}^{\mathrm{8}} +\mathrm{1}}\:\mathrm{which}\:\mathrm{is}\:\mathrm{possible}\:\mathrm{but}\:\mathrm{it}'\mathrm{s}\:\mathrm{no}\:\mathrm{fun}\:\mathrm{dealing} \\ $$$$\mathrm{with}\:\mathrm{the}\:\mathrm{factors} \\ $$