Find, in the form \(\mathbf { r } = \mathbf { a } + t \mathbf { b }\), an equation of the line \(l\) through the points ( \(4,2,7\) ) and ( \(5 , - 4 , - 1\) ).
Find the acute angle between the line \(l\) and a line in the direction of the vector \(\left( \begin{array} { l } 1 2 3 \end{array} \right)\).