Direction ratios of the given lines are respectively < 2, 2, 1 > and < 4, 1, 8 > Let θ be the angle between the given lines, then where $a_1, b_1, c_1$ and $a_2, b_2, c_2$ are direction ratios $\cos \theta$ $= \frac{\left| 2\times 4+2\times 1+1\times 8 \right|}{\sqrt{2^2+2^2+1^2} \sqrt{4^2+1^2+8^2}}$ $= \frac{18}{\sqrt{9} \sqrt{81}} = \frac{2}{3}$ $\Rightarrow \theta = \cos^{-1} \frac{2}{3}$