Jokes - Have fun

[Camillo]

An astronomer, a physicist, and a mathematician were on vacation in Scotland. From a train window, they saw a black sheep in the middle of a field. "How interesting", observed the astronomer, "all Scottish sheep are black." To which the physicist replied "No, no! Some Scottish sheep are black!" The mathematician gazed heavenward, then intoned,
"In Scotland, there exists at least one field, containing at least one sheep, at least one side of which is black."



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Two physicists were riding in a hot air balloon and were blown off course sailing over a mountain trail. They were completely lost, when they spotted a jogger running on the trail and shouted "Can you tell us where we are?" After a few minutes, the jogger yelled back, "You're up in a balloon." One physicist turned to the other, "Just our luck to run into a mathematician". "How did you know he was a mathematician?" "Well, in the first place he took a long time to answer; second, his answer was 100% correct, and third, it was totally useless."

[Eredir]

Nice ones.

How to prove it. Guide for lecturers.

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

Proof by forward reference:
Reference is usually to a forthcoming paper of the author, which is often not as forthcoming as at first.

Proof by funding:
How could three different government agencies be wrong?

Proof by example:
The author gives only the case n = 2 and suggests that it contains most of the ideas of the general proof.

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

Proof by deferral:
"We'll prove this later in the course".

Proof by picture:
A more convincing form of proof by example. Combines well with proof by omission.

Proof by intimidation:
"Trivial."

Proof by adverb:
"As is quite clear, the elementary aforementioned statement is obviously valid."

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

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

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

Proof by obfuscation:
A long plotless sequence of true and/or meaningless syntactically related statements.

Proof by wishful citation:
The author cites the negation, converse, or generalization of a theorem from the literature to support his claims.

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 inaccessible literature:
The author cites a simple corollary of a theorem to be found in a privately circulated memoir of the Slovenian Philological Society, 1883.

Proof by importance:
A large body of useful consequences all follow from the proposition in question.

Proof by accumulated evidence:
Long and diligent search has not revealed a counterexample.

Proof by cosmology:
The negation of the proposition is unimaginable or meaningless. Popular for proofs of the existence of God.

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.

Proof by metaproof:
A method is given to construct the desired proof. The correctness of the method is proved by any of these techniques.

Proof by vehement assertion:
It is useful to have some kind of authority relation to the audience.

Proof by ghost reference:
Nothing even remotely resembling the cited theorem appears in the reference given.

Proof by semantic shift:
Some of the standard but inconvenient definitions are changed for the statement of the result.

Proof by appeal to intuition:
Cloud-shaped drawings frequently help here.