The angle between the lines whose direction cosines satisfy the equations `l + m + n = 0 and l^(2) = m^(2) + n^(2)` is

The angle between the lines whose direction cosines satisfy the equation l+m+n=0 and l^(2)=m^(2)+n^(2) is

Find the angle between the lines whose direction cosines satisfy the equaitons l + m + n = 0, l^(2) + m^(2) - n^(2) = 0 .

Find the angle between the lines whose direction cosines are given by the equation l + m + n = 0 and l^2 + m^2 - n^2 = 0.