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 the point on the line (1) with position vector
and T be the point on the line (2) with position vector 

Now,




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

Now. S.D. = Projection of
= Projection of 


and

Comparing these equations with



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



Now,






Let


If



Now. S.D. = Projection of



