3.
\begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{106e8e6b-912d-45ef-89e9-12ffc04bfd25-06_369_661_155_760}
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\caption{Figure 1}
\end{figure}
The shape \(A B C D O A\), as shown in Figure 1, consists of a sector \(C O D\) of a circle centre \(O\) joined to a sector \(A O B\) of a different circle, also centre \(O\).
Given that arc length \(C D = 3 \mathrm {~cm} , \angle C O D = 0.4\) radians and \(A O D\) is a straight line of length 12 cm ,
- find the length of \(O D\),
- find the area of the shaded sector \(A O B\).