Question
Find the shortest distance between the lines:

and
.
Solution
The equations of the two lines are
...(1)
and
...(2)
Comparing these equations with



Let S be point on line (1) with position vector
and T be point on line (2) with position vector
so that


Now,


Let
be the S.D. vector between given lines. Therefore, it is parallel to 
If
is a unit vector along
, then

Now S.D. = Projection of
= Projection of 


and

Comparing these equations with



Let S be point on line (1) with position vector




Now,




Let


If



Now S.D. = Projection of


