\subsection{Trigonometry \& Linear Algebra}
\shortdefinition[Rule of cosines] $c^2 = a^2 + b^2 - 2ab \cos(\gamma)$

% TODO: Add convenient results (such as cos2 + sin2 = 1)
\shortdefinition[Orthogonal vec] $v^\top w = 0$;
\shortdefinition[Vec Line Eq] $\vec{p} + \lambda \vec{d}$

\shortdefinition[Determinant] $ad - bc$ for mat $[a, b; c, d]$

\shortdefinition[Eigenvalues] Solve $\det(M - \lambda I) = 0$