**Mathematical Folk Humor, thanks to P. Renteln and A. Dundes****
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A mathematics professor was lecturing to a class of students. As he wrote something on the board, he said to the class:**

"Of course, this is immediately obvious."

Upon seeing the blank stares of the students, he turned back to contemplate what he had just written. He began to pace back and forth, deep in thought. After about ten minutes, just as the silence was beginning to become uncomfortable, he brightened, turned to the class and said:

"Yes, it IS obvious."

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Question: How many Bourbakists does it take to screw in a light-bulb?**

Answer: Changing a lightbulb is a special case of a more general theorem concerning the maintenance and repair of an electrical system. To establish upper and lower bounds for the number of persons required, we must determine whether the sufficient conditions of Lemma 2.1 (Availibility of personnel) and those of Corollary 2.3.55 (Motivation of personnel) apply. If, and only if, these conditions are met, we derive the result by an application of the theorems in Section 3.1123. The resulting upper bound is, of course, a result in an abstract measure space, in the weak-* topology.

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Question: How many analysts does it take to screw in a lightbulb?**

Answer: Three. One to prove existence, one to prove uniqueness, and one to derive a nonconstructive algorithm to do it.

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Two mathematicians are in a bar. The first one says to the second that the average person knows very little about basic mathematics. The second one disagrees. The first mathematician goes off to the washroom, and in his absence the second calls over the waitress. He tells her that in a few minutes, after his friend has returned, he will call her over and ask her a question. All she has to do is answer "one third x cubed". She repeats "one thir-dex cue?" He repeats "one third x cubed". She says "one thir dex cuebd?" "Yes, that's right." So she agrees, and goes off mumbling to herself "one thir dex cuebd, one thir dex cuebd". The first guy returns and the second proposes a bet to prove his point, that most people do know something about basic math. He says he will ask the blonde waitress an integral, and the first laughingly agrees. The second man calls over the waitress and asks "what is the integral of x squared?" The waitress says "one third x cubed" and while walking away, turns back and says over her shoulder "plus a constant!"**

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Question: Why did the chicken cross the road?**

Gödel: It cannot be proved whether the chicken crossed the road.

Erdös: It was forced to do so by the chicken-hole principle.

Fermat: It did not fit on the margin on this side.

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A bunch of Polish scientists decided to flee their country by highjacking an airliner and forcing the pilot to fly them to a western country. They forced their way on board a large passenger jet, and found there was no pilot on board. One of the scientists suggested that since he was an experimentalist, he would try to fly the aircraft. He sat down at the controls and tried to figure them out. Armed men surrounded the jet. The would-be pilot's friends cried out:**

"Hurry!!"

The experimentalist calmly replied:

"Have patience. I'm just a simple pole in a complex plane."

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Excuses for not doing homework:**

- I could only get arbitrarily close to my textbook. I couldn't actually reach it.

- I have the proof, but there isn't room to write it in this margin.

- I could have sworn I put the homework inside a Klein bottle, but this morning I couldn't find it.

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How to prove theorems:**

Proof by vigorous handwaving: works well in a classroom or seminar setting.

Proof by example: give only the case n=2 and suggest that it contains most of the ideas of the general proof.

Proof by omission: "The reader may easily supply the details." "The other 253 cases are analogous."

Proof by intimidation: "Trivial."

Proof by cumbersome notation: best done with access to at least four alphabets and special symbols.

Proof by seduction: "Convince yourself that this is true!"

Proof by exhaustion: an issue or two of a journal devoted to your proof is useful.

Proof by eminent authority: "I saw Karp in the elevator and he said it was probably NP-complete."

Proof by personal communication: "Eight-dimensional colored cycle stripping is NP-complete [Karp, personal communication]."

Proof by reduction to the wrong problem: "To see that infinite-dimensional colored cycle stripping is decidable, we reduce it to the halting problem."

Proof by reference to an inaccessible literature: cite a simple corollary of a theorem to be found in a privately circulated memoir of the Slovenian Philological Society, 1883.

Proof by mutual reference: in reference A, Theorem 5 is said to follow from Theorem 3 in reference B, which is shown to follow from Corollary 6.2 in reference C, which is an easy consequence of Theorem 5 in reference A.

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Theorem: All positive integers are interesting.**

Proof. Assume the contrary. Then there is a lowest noninteresting positive integer. But, hey, that's pretty interesting! A contradiction.

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The snakes asked Noah to cut down some trees for them.**

"Why?" asked Noah.

"We're adders, so we need logs to multiply."

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An engineer, a physicist and a mathematician are staying in a hotel.**

The engineer wakes up and smells smoke. He goes out in the hallway and sees a fire, so he fills a trash can with water and douses the fire. He goes back to bed.

The physicist wakes up and smells smoke. He goes out in the hallway and sees a fire, so he goes to a fire hose and after calculating the flame velocity, distance, water pressure, trajectory, and so forth, extinguishes the fire with the minimum amount of water and energy needed. He goes back to bed.

The mathematician wakes up and smells smoke. He goes out in the hallway and sees a fire. He sees the fire hose, thinks for a moment and then says: "A solution exists." He goes back to bed.

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There was a mad scientist who kidnapped three colleagues, an engineer, a physicist and a mathematician, and locked each of them in separate cells with plenty of canned food and water, but no can opener. A month later, returning, he found the engineer's cell empty. The engineer had constructed a can opener from pocket trash, used aluminium shavings and dried sugar to make an explosive, and escaped. The physicist had worked out the angle necessary to knock the lids off the tin cans by throwing them against the wall. She was developing a good pitching arm and a new quantum theory. The mathematician had stacked the unopened cans into a surprising solution to the kissing problem; his desiccated corpse was propped calmly against a wall, and this was inscribed on the floor in blood:**

Theorem. If I can't open these cans, I"ll die. Proof. Assume the opposite...

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