JEE Main 2021 (Online) 20th July Morning ShiftQuestion 346
If the shortest distance between the lines $\vec r_1=\alpha\hat i+2\hat j+2\hat k+\lambda\left(\hat i-2\hat j+2\hat k\right)$, $\lambda\in R$, $\alpha>0$ and $\vec r_2=-4\hat i-\hat k+\mu\left(3\hat i-2\hat j-2\hat k\right)$, $\mu\in R$ is $9$, then $\alpha$ is equal to
3D Geometry