[; R_{\theta}(\underline{v}) = \underline{\underline{R}}_{\theta} \underline{v} ;]
[; R_{\theta}(\underline{v}_1+\underline{v}_2) = R_{\theta}(\underline{v}_1) + R_{\theta}(\underline{v}_2) ;]
[; \underline{\underline{R}}_{\theta} = \begin{pmatrix} \cos{\theta} & -\sin{\theta}\\ \sin{\theta} & \cos{\theta}\\ \end{pmatrix} ;]
[; \underline{\underline{R}}_{\theta_1} \underline{\underline{R}}_{\theta_2} = \underline{\underline{R}}_{\theta_1+\theta_2} \quad \Rightarrow ;]
[; \underline{\underline{R}}_{\theta}^n = \underline{\underline{R}}_{n\theta}, \quad n \in \mathbb{Z} ;]
[; \underline{\underline{R}}_{\theta}^{-1} = \underline{\underline{R}}_{\theta}^T = \underline{\underline{R}}_{-\theta} ;]