Also, isn't this a great example of "when you have a hammer, everything looks like a nail" ? To explain this I would first and foremost use a picture, where th

Also, isn't this a great example of "when you have a hammer, everything looks like a nail" ? To explain this I would first and foremost use a picture, where the 3 cases : parallel, identical, intersection can be intuitively seen (using our visual system, rather than our language system), with merely a glance.