Question

If a line has the direction ratio -18,12and-4, then what are its direction cosines?

Answer 1

If a line has direction ratios of -18,12and-4,then its direction cosines are
$-\frac{18}{\sqrt{(-18)^2}}$+(12)2+(-4)2,$-\frac{12}{\sqrt{(-18)^2}}$+(12)2+(-4)2,$-\frac{-4}{\sqrt{(-18)^2}}$+(12)2+(-4)2
i.e.,$-\frac{18}{22}$,$\frac{12}{22}$,$-\frac{4}{22}$
$-\frac{9}{11}$,$\frac{6}{11}$,$-\frac{2}{11}$
Thus,the direction cosines are $-\frac{9}{11}$,$\frac{6}{11}$and$-\frac{2}{11}$.