Two lines have equations $$\(\mathbf{r}=\left(\begin{array}{l}1 \\ 3 \\ 2\end{array}\right)+s\left(\begin{array}{r}2 \\ -1 \\ 3\end{array}\right)\)$$ and $$\(\mathbf{r}=\left(\begin{array}{l}2 \\ 1 \\ 4\end{array}\right)+t\left(\begin{array}{r}1 \\ -1 \\ 4\end{array}\right)\)$$. Find the acute angle between the directions of the two lines. ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................

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