5 Find the direction cosines of the sides of the triangle whose vertices are
(3, 5, – 4), (– 1, 1, 2) and (– 5, – 5, – 2) © NCERT
not to be republished
 MATHEMATI CS
468
11 3 Equation of a Line in Space
We have studied equation of  lines in two dimensions in Class XI, we shall now study
the vector and cartesian equations of a line in space