My professor for my this particular class definitely told this joke. He had quite a few bad ones lined up from lectures that I definitely put into comic form. He was a good guy, that professor.
Not that I remember what class it was. >_> Had something to do with magnetic fields, though. Here’s the Wikipedia article on dot products, in case you’re interested.
And conveniently, with Abby having a physics major, I felt that she would more likely be in the same math-type classes as Sasha was. As if it was planned that way or something.