Question
Find the shortest distance between the lines:

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

We get,

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


and

Comparing these equations with

We get,

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




Now,



Let


If


then

Now S.D. = Projection of


