PlanetPhysics/Euler 312 Sequence

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

$$ R_{312}(\phi, \theta, \psi) = R_2(\psi) R_1(\theta) R_3(\phi) $$ \\

The rotation matrices are

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

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

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

Carrying out the multiplication from right to left \\

$$ R_1(\theta)R_3(\phi) = \left[ \begin{matrix} 1 & 0 & 0 \\ 0 & c_{\theta} & s_{\theta} \\ 0 & -s_{\theta} & c_{\theta} \end{matrix} \right] \left[ \begin{matrix} c_{\phi} & s_{\phi} & 0 \\ -s_{\phi} & c_{\phi} & 0 \\ 0 & 0 & 1 \end{matrix} \right] = \left[  \begin{matrix} c_{\phi} & s_{\phi} & 0 \\ -s_{\phi} c_{\theta} & c_{\theta} c_{\phi} & s_{\theta} \\ s_{\theta} s_{\phi} & -s_{\theta} c_{\phi} & c_{\theta} \end{matrix} \right] $$ \\

Finaly leaving us with the Euler 312 sequence \\

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