Write the formula for the shortest distance between the lines ` -> r= -> a_1+lambda -> b\ a n d\ -> r= -> a_2+mu -> bdot\ `

Explanation

We have `vec(r)=vec(a_1)+lambda vec(b)` and `vec(r)=vec(a_2)+mu vec(b)`

Then the shortest distance between the lines is given by

`d=|((vec(a_2)-vec(a_1))xx (vec(b)))/|vec(b)||`

`d=|(vec(a_2)-vec(a_1)) xx vec(b)|/|vec(b)|`