The angle between the lines whose direction cosines are connected by the relations l + m + n = 0 and 2lm + 2nl - mn = 0 is .

I am not able to understand this question , do cosine ratios of both the lines satisfy the above two equations or each one separately ?
Please solve it completely too .

Question

The angle between the lines whose direction cosines are connected by the relations l + m + n = 0 and 2lm + 2nl - mn = 0 is .

I am not able to understand this question , do cosine ratios of both the lines satisfy the above two equations or each one separately ? 
Please solve it completely too .

perl · Answer

are these lines defined by vector equations?

alekos · Answer

there's got to be more to this question

perl · Answer

yes, im not sure what l, m,n stand for exactly