The direction cosines of two lines are given by the equations `3m+n+5l=0, 6nl-2lm+5mn=0.` find the angle between them

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

If the direction cosines of two lines are connected by the equations l+m+n=0 and l^(2) + m^(2) -n^(2)=0 , then the angle between these lines is of measure

If the direction cosines of two lines given by the equations p m+qn+rl=0 and lm+mn+nl=0 , prove that the lines are parallel if p^2+q^2+r^2=2(pq+qr+rp) and perpendicular if pq+qr+rp=0

The direction cosines of two lines are connected by relation l+m+n=0 and 4l is the harmonic mean between m and n. Then,

If the direction ratio of two lines are given by 3lm-4ln+mn=0 and l+2m+3n=0 , then the angle between the lines, is

Find the direction colatines of the lines, connected by the relations: l+m+n=0 and 2lm+2ln-mn=0.