\subsection{Inverse Kinematics (IK)}
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    \includegraphics[width=0.35\columnwidth]{assets/inverse-kinematics.png}
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\bi{Option}: Solve FK for angles.\\
\bi{Better}: Law of cosine with polar coordinates. Compute angle using cosine rule,
$\theta_1 = \varphi \pm \alpha$, $\theta_2 = \pm(\pi - \beta)$
(Positive for {\color{ForestGreen} Elbow Down}, Neg. for {\color{red} Elbow Up})

\bi{Extension to 6R}:
1. Waist: spherical coords (2 sol.)\\
2. 2 sols from 2R for shoulder + elbow\\
3. Solve for wrist joints (no infl. on pos)

\bi{For Inv. velocity}: $\vec{\dot{\theta}} = J_S^{-1}(\vec{\theta}) {_W} \vec{t}_{WE}$