Question

The direction cosines of the line joining points (4, 3, –5) and (–2, 1, –8) are ______________.

Answer 1

For points given by (4, 3, –5) and (–2, 1, –8) line joining these points is $6\hat{j}+2\hat{j}+3\hat{k}$

$$\begin{gathered} \therefore \mathrm{Magnitude}\mathrm{is}\mathrm{give}\mathrm{by}\sqrt{36+4+9} \\ =\sqrt{49} \\ =7 \end{gathered}$$
Hence direction cosines are given by $\frac{6}{7},\frac{2}{7},\frac{3}{7}$