My first thought is that my discrete math professor isn’t from a friendly place.
There this math concept, that I’ve always known as the sandwich theorem, that says that if two curvy lines that run side-by-side meet and continue along together, then any line that always stays between these two lines meets as well and continues along with the other two lines. That third line is sandwiched between the other two.
Our prof explained it this way: suppose you are walking around and you see a policeman. Well, you clearly wouldn’t want to continue in that direction so you would go in the other direction. Well, suppose you again see a policeman! Then you would immediately head in the other direction but the first policeman is there and now he is closer! And so you continue back and forth between them as they come closer together until you are between the two policemen. You can be no where else.
Or as Luther put it: “Here I stand, I can do no other.”
This was received deadpan by his audience, my classmates. As was his explanation of Fibonacci’s bunnies.
Fibonnaci was an Italian mathematician who, according to our sensei, is most famous for counting rabbits. Wikipedia supports this assertion by the way, but phrases it a little more delicately.
“Suppose you have one rabbit and it becomes fertile. No wait, suppose you have two rabbits and one becomes fertile. Pretty soon you have three rabbits. Now if this one,” he stabs at one of three dots on the black board, “becomes fertile, and this one becomes fertile,” a second stab at the blackboard, “now you have five rabbits.” There is a question and he goes through the whole thing again. “two rabbits, one fertile, three rabbits, two fertile, …” There is a second question and its even faster now: “fertile, fertile, fertile…”
The numbers are duly written: 1, 1, 2, 3, 5, 8, … and I have no doubt most people followed the jist of things but one of the class is hearing impaired. They have a translator who, in sign, relays what is being said to the student. The poor translator (whom, of the two was facing me) looked absolutely lost but nonetheless was signing furiously.
And so today’s lesson was really on sign language. 2, fertile! 3, fertile! 5, fertile!
