A(–1,2,–3) ,B(5,0,–6) and C(0,4,–1) are the vertices of a triangle. The dr’s of the internal bisector of$\angle$BAC are

A = (–1, 2, –3), B = (5, 0, –6), C(0, 4, –1)
$\Rightarrow$D divides BC in the ratio 7:3
$$\begin{gathered} \Rightarrow D=(\frac{15}{10},\frac{28}{10},\frac{-25}{10}) \\ \Rightarrow d.r\text{'}s of \overline{\mathrm{AD}}=\left(\frac{15}{10}+1,\frac{28}{10}-2,\frac{-25}{10}+3\right) \\ =(\frac{25}{10} ,\frac{8}{10} ,\frac{5}{10}) \\ =(25,8,5) \end{gathered}$$