An oddly intuitive method to finding the distance between two skew lines in 3 space.
We begin by considering two lines. Namely, and . I now plot these two lines in 3 space in order to justify their skewness i.e. They do not intersect and are not parallel.
I now introduce a new function and this is defined as the distance between the two lines i.e. . We now work with this equation to derive a general method for calculating the distance between two skew lines.
Before we begin, recall that
Now,
I now bring in some Calculus. We use the fact that minimizing a function is the same as minimizing the square of that function (does not always hold but it holds here because we are dealing with a distance function that is non-negative and monotonic). Hence, we do the following:
We now take the partial derivatives with respect to s and t and we set it equal to zero. This is as follows.
Solving the system of linear equations we arrive at and .…