\begin{enumerate}
\item\label{05-trigo-08-corr-q1} $\begin{aligned}[t]
\angleor{AD}{AB} & \angleor{AD}{AC}+\angleor{AC}{AB}\\
& = -\dfrac{\pi}{3}-\dfrac{\pi}{2}\\
\Aboxed{\angleor{AD}{AB} & = -\dfrac{5\pi}{6}}
\end{aligned}$

\item $\begin{aligned}[t]
\angleor{DC}{AC} & = \angleor{CD}{CA}\quad\text{ car } (-\vv{u},-\vv{v})=(\vv{u},\vv{v})\\
\Aboxed{\angleor{DC}{AC} & = \dfrac{\pi}{3}}
\end{aligned}$

\item $\begin{aligned}[t]
\angleor{DC}{BA} & = \angleor{DC}{DA}+\angleor{DA}{BA}\\
& = -\dfrac{\pi}{3}+\angleor{AD}{AB}\\
& = -\dfrac{\pi}{3}-\dfrac{5\pi}{6}\quad\text{d'après \ref{05-trigo-08-corr-q1}}\\
 & = -\dfrac{7\pi}{6}\quad\text{(qui n'est pas une mesure principale car }-\dfrac{7\pi}{6}<-\pi)\\
 & = -\dfrac{7\pi}{6}+2\pi\\
 \Aboxed{\angleor{DC}{BA} & = \dfrac{5\pi}{6}}
\end{aligned} $
\end{enumerate}