Question

If a line makes angles 90°,135° and 45° with x,y and z-axes respectively, find its direction cosines.

Answer 1

Let direction cosines of the line l,m and n.
l=cos90°=0
m=cos135°=$-\frac{1}{\sqrt 2}$
n=cos45°=$\frac{1}{\sqrt 2}$
Therefore, the direction cosines of the line are 0,$-\frac{1}{\sqrt 2}$and$\frac{1}{\sqrt 2}$.