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 Let a, b, c be direction ratios of a line and let l, m and n be the direction cosines
(d