The angle between the straight lines r⃗ =(2−3t)i⃗ +(1+2t)j⃗ +(2+6t)k⃗  and r⃗ =(1+4s)i⃗ +(2−s)j⃗ +(8s−1)k⃗ is

[d] L1=r⃗ 1=2i⃗ +j⃗ +2k⃗ +t(−3i⃗ +2j⃗ +6k⃗ ) L2=r⃗ 2=(i⃗ +2j⃗ −k⃗ )+s(4i⃗ −j⃗ +8k⃗ ) ∴ Angle between L1 and L2 is given by cosθ=(−3i⃗ +2j⃗ +6k⃗ ).(4i⃗ −j⃗ +8k⃗ )9+4+36−−−−−−−−√16+1+64−−−−−−−−−√ =−12−2+4849−−√81−−√=347×9=3463 ⇒θ=cos−1(3463)