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\begin{equation*}
 \begin{bmatrix}
    (M+m) & - ml\cos\theta \\
    - m l \cos\theta & (J+ml^2)
   \end{bmatrix} \begin{bmatrix} \ddot p \\ \ddot\theta  \end{bmatrix}
  + \begin{bmatrix} c \dot p + ml \sin\theta\, \dot\theta^2 \\
    \underline{-mgl\sin\theta} + \gamma \dot\theta
  \end{bmatrix} = \begin{bmatrix} F \\ 0 \end{bmatrix},
\end{equation*}
\end{document}