If the proof of a theorem is not immediately apparent, it may be because you are trying the wrong approach. Below are some effective methods of proof that may aim you in the right direction.

* Proof by Obviousness: “The proof is so clear that it need not be mentioned.”

* Proof by General Agreement: “All in Favor?…”

* Proof by Imagination: “Well, We’ll pretend its true.”

* Proof by Convenience: “It would be very nice if it were true, so …”

* Proof by Necessity: “It had better be true or the whole structure of mathematics would crumble to the ground.”

* Proof by Plausibility: “It sounds good so it must be true.”

* Proof by Intimidation: “Don’t be stupid, of course it’s true.”

* Proof by Lack of Sufficient Time: “Because of the time constraint, I’ll leave the proof to you.”

* Proof by Postponement: “The proof for this is so long and arduous, so it is given in the appendix.”

* Proof by Accident: “Hey, what have we here?”

* Proof by Insignificance: “Who really cares anyway?”

* Proof by Mumbo-Jumbo: ” For any epsilon> 0 there exists a corresponding delta > 0 s.t. f(x) − L < epsilon whenever x − a < delta”

* Proof by Profanity: (example omitted)

* Proof by Definition: “We’ll define it to be true.”

* Proof by Tautology: “It’s true because it’s true.”

* Proof by Plagiarism: “As we see on page 238 …”

* Proof by Lost Reference: “I know I saw this somewhere …”

* Proof by Calculus: “This proof requires calculus, so we’ll skip it.”

* Proof by Terror: When intimidation fails …

* Proof by Lack of Interest: “Does anyone really want to see this?”

* Proof by Illegibility: ” ¥ ª Ð Þ þæ”

* Proof by Logic: “If it is on the problem sheet, then it must be true.”

* Proof by Majority Rule: Only to be used if General Agreement is impossible.

* Proof by Clever Variable Choice: “Let A be the number such that this proof works.”

* Proof by Tessellation: “This proof is just the same as the last.”

* Proof by Divine Word: “And the Lord said, ‘Let it be true,’ and it came to pass.”

* Proof by Stubbornness: “I don’t care what you say! It is true!”

* Proof by Simplification: “This proof reduces to the statement, 1 + 1 = 2.”

* Proof by Hasty Generalization: “Well, it works for 17, so it works for all reals.”

* Proof by Deception: “Now everyone turn their backs …”

* Proof by Supplication: “Oh please, let it be true.”

* Proof by Poor Analogy: “Well, it’s just like …”

* Proof by Avoidance: Limit of Proof by Postponement as t approaches infinity.

* Proof by Design: “If it’s not true in today’s math, invent a new system in which it is.”

* Proof by Intuition: “I just have this gut feeling …”

* Proof by Authority: “Well, Bill Gates says it’s true, so it must be.”

* Proof by Vigorous Assertion: “And I REALLY MEAN THAT!”

* Proof by A.F.K.T. Theorem: “Any Fool Knows That!”

* Proof by vigorous handwaving: Works well in a classroom.

* Proof by seduction: “Convince yourself that this is true!”

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

* Proof by Divine Intervention: “Then a miracle occurs …”

* 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 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 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.

This post was completely taken from this website http://www.onlinemathlearning.com/math-jokes-mathematical-proofs.html