Vector dot product

Using dot product on $\mathbb{R}^{6}$, find an angle between vectors $\begin{pmatrix}2&1&-1& 0&-2&1\end{pmatrix}^{\mathsf{T}}$ and $\begin{pmatrix}-1&0&2& 1&-2&-1\end{pmatrix}^{\mathsf{T}}$.