If a line has the direction ratios '-18,(12) ,-4', then what are its directión cosines?

Answer

The d.c.'s are `(-18)/(sqrt(18^2+12^2+(-4)^2), (12)/(sqrt(18^2+12^2+(-4)^2), (-4)/(sqrt(18^2+12^2+(-14)^2)`
If a, b, c are the direction ratios of a line then its d.c.'s are `(a)/(sqrt(a^2+b^2+c^2), (b)/(sqrt(a^2+b^2+c^2), (c)/(sqrt(a^2+b^2+c^2)`
i.e., `(-18)/22, (12)/22, (-4)/22` i.e., `(-9)/11, (6)/11, (-2)/11`