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Mixali Mou,

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Let $\vec a_1$ be the acceleration of the wedge, $\vec a_2$
be the acceleration of the block.

The answers are (I hope) the following:

\begin{itemize}

\item[\bf A.] 
$a_1 = g \sin (\alpha)\cos(\alpha) \ \frac {m}{\sin^2 (\alpha) m  + M} \ 
$




\end{itemize}


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