The variables \(x\), \(y\) and \(u\) are such that \(y=\tan u\) and \(x=u^3+1\).

(i) State the rate of change of \(y\) with respect to \(u\).

(ii) Hence find the rate of change of \(y\) with respect to \(x\), giving your answer in terms of \(x\).