Now take one of the directed lines from the origin and find its direction cosines as two
parallel line have same set of direction cosines Any three numbers which are proportional to the direction cosines of a line are
called the direction ratios of the line If l, m, n are direction cosines and a, b, c are
direction ratios of a line, then a = λl, b=λm and c = λn, for any nonzero λ ∈ R �Note   Some authors also call direction ratios as direction numbers