The direction cosines I, m, n of two lines are connected by the relations l+m+n=0 lm =0 , then the angle between them is

Step-by-step solution

Given, 1+m+n=0 (i) and lm =0 Either m=0 or l=0 If l=0 , then put in Eq. (i), we get m=-n Direction ratios are 0,-n, n i.e. 0,-1,1 If m=0 , then put in Eq. (i), we get l=-n Direction ratios are -n, 0, n i.e. -1,0,1 = 0 (-1)+(-1) 0+1 1 (0)^2+(-1)^2+(1)^2 (-1)^2+(0)^2+(1)^2 = 1 2 = 3