(i) Use de Moivre's theorem to prove that
\(\tan 4 \theta=\frac{4 \tan \theta-4 \tan ^{3} \theta}{1-6 \tan ^{2} \theta+\tan ^{4} \theta}\)

(ii) Hence find the solutions of the equation
\(t^{4}-4 t^{3}-6 t^{2}+4 t+1=0\)
giving your answers in the form \(\tan k \pi\), where \(k\) is a rational number.