PlanetPhysics/Euler 231 Sequence

For more info on Euler Sequences, notation and convention see the generic entry on Euler angle sequences.

$$ R_{231}(\phi, \theta, \psi) = R_1(\psi) R_3(\theta) R_2(\phi) $$ \\

The rotation matrices are

$$ R_1(\psi) = \left[ \begin{matrix} 1 & 0 & 0 \\ 0 & c_{\psi} & s_{\psi} \\ 0 & -s_{\psi} & c_{\psi} \end{matrix} \right] $$

$$ R_3(\theta) = \left[ \begin{matrix} c_{\theta} & s_{\theta} & 0 \\ -s_{\theta} & c_{\theta} & 0 \\ 0 & 0 & 1 \end{matrix} \right] $$

$$ R_2(\phi) = \left[ \begin{matrix} c_{\phi} & 0 & -s_{\phi} \\ 0 & 1 & 0 \\ s_{\phi} & 0 & c_{\phi} \end{matrix} \right] $$

Carrying out the matrix multiplication from right to left \\

$$ R_3(\theta)R_2(\phi) = \left[ \begin{matrix} c_{\theta} & s_{\theta} & 0 \\ -s_{\theta} & c_{\theta} & 0 \\ 0 & 0 & 1 \end{matrix} \right] \left[ \begin{matrix} c_{\phi} & 0 & -s_{\phi} \\ 0 & 1 & 0 \\ s_{\phi} & 0 & c_{\phi} \end{matrix} \right] = \left[ \begin{matrix} c_{\theta} c_{\phi} & s_{\theta} & -c_{\theta} s_{\phi} \\ -s_{\theta} c_{\phi} & c_{\theta} & s_{\theta} s_{\phi} \\ s_{\phi} & 0 & c_{\phi} \end{matrix} \right] $$ \\

Finally leaving us with the Euler 231 sequence \\

$$ R_1(\psi)R_3(\theta)R_2(\phi) = \left[ \begin{matrix} c_{\theta} c_{\phi} & s_{\theta} & -c_{\theta} s_{\phi}  \\ -c_{\psi} s_{\theta} c_{\phi} + s_{\psi} s_{\phi} & c_{\psi} c_{\theta} & c_{\psi} s_{\theta} s_{\phi} + s_{\psi} c_{\phi} \\ s_{\psi} s_{\theta} c_{\phi} + c_{\psi} s_{\phi} & -s_{\psi} c_{\theta} & -s_{\psi} s_{\theta} s_{\phi} +c_{\psi} c_{\phi} \end{matrix} \right] $$