Exprimer la matrice issue de la combinaison des rotations suivantes :

\begin{cases} \begin{pmatrix} \bold a_1' \\ \bold a_2' \\ \bold a_3' \end{pmatrix} = [T(\theta_3)]_3 \ \begin{pmatrix} \bold a_1 \\ \bold a_2 \\ \bold a_3 \end{pmatrix} \\ \begin{pmatrix} \bold a_1'' \\ \bold a_2'' \\ \bold a_3'' \end{pmatrix} = [T(\theta_2)]_2 \ \begin{pmatrix} \bold a_1' \\ \bold a_2' \\ \bold a_3' \end{pmatrix} \\ \begin{pmatrix} \bold b_1 \\ \bold b_2 \\ \bold b_3 \end{pmatrix} = [T(\theta_1)]_1 \ \begin{pmatrix} \bold a_1'' \\ \bold a_2'' \\ \bold a_3'' \end{pmatrix} \end{cases}