$$\begin{align*} i &= \sqrt{2} I \sin(wt + \psi_i) \\ \\ \\ u = R i &= \sqrt{2} RI \sin(wt + \psi_i) \\ \\ u &= \sqrt{2} U \sin(wt + \psi_i) \end{align*}$$

As you can see, here not much to say.