4.
\begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{c9fff982-d38b-42ff-ab4e-08008439a95b-06_456_1273_262_388}
\captionsetup{labelformat=empty}
\caption{Figure 1}
\end{figure}
Figure 1 shows the curve \(C\) with polar equation
$$r = 2 \cos 2 \theta , \quad 0 \leqslant \theta \leqslant \frac { \pi } { 4 }$$
The line \(l\) is parallel to the initial line and is a tangent to \(C\).
Find an equation of \(l\), giving your answer in the form \(r = \mathrm { f } ( \theta )\).