Explanation:
A Given, \(\mathrm{A}=(3,4,5), \mathrm{P}=(-1,2,4), \mathrm{B}=(4,6,3)\) and \(\mathrm{Q}=(1,0,5)\) \(\therefore\) Direction ratio of line \(\mathrm{AB}\) are \((4-3),(6-4),(3-5)\) \(=(1,2,-2)\)
And direction ratio of line PQ are \((1+1),(0-2)\), \((5-\) \(4)=(2,-2,1)\)
\(\therefore\) Direction cosine of line -
\(\mathrm{PQ} =\frac{2}{\sqrt{2^2+(-2)^2+1}}, \frac{-2}{\sqrt{2^2+(-2)^2+1}}, \frac{1}{\sqrt{2^2+(-2)^2+1}}\)
\(=\frac{2}{3}, \frac{-2}{3}, \frac{1}{3}\)
\(\therefore\) Projection of line segment \(\mathrm{AB}\) on the line \(\mathrm{PQ}\) is
\(\left \vert\frac{2}{3}(1)+\left(\frac{-2}{3}\right)(2)+\left(\frac{1}{3}\right)(-2)\right \vert=\frac{4}{3}\)