I came across the following representation of a rotation matrix given an axis of rotation $\begin{bmatrix}n_1 & n_2 & n_3\end{bmatrix}$ and an angle $\theta$.
I'm trying to figure out where it comes from, and first thought to check the Rodrigues rotation formula.
$R = I + \sin \theta K + (1 - \cos \theta)K^2$
where $K$ is the skew symmetric matrix of the axis of rotation.
I used MATLAB's symbolic math library to compute the Rodrigues formula given $K$ and $\theta$ to see if it matches the expression in the paper - but it's indeed different.
Anyone have an idea of where equation (8) comes from?