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36 ways of mathematical proof

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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 it’s true…”
Proof by convenience: “It would be very nice if it were true, so…”
Proof by necessity: “It had better be true, or the entire 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 constrait, I’ll leave the proof to you.”
Proof by postponement: “The proof for this is long and arduous, so it is given to you in the appendix.”
Proof by accident: “Hey, what have we here?!”
Proof by insignificance: “Who really cares anyway?”
Proof by mumbo-jumbo:
Proof by profanity: (example omitted)
Proof by definition: “We define it to be true.”
Proof by tautology: “It’s true because it’s true.”
Proof by plagarism: “As we see on page 289,…”
Proof by lost reference: “I know I saw it 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:
Proof by logic: “If it is on the problem sheet, 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 the same as the last.”
Proof by divine word: “…And the Lord said, ‘Let it be true,’ and it was true.”
Proof by stubbornness: “I don’t care what you say- it is true.”
Proof by simplification: “This proof reduced 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 it approaches infinity
Proof by design: If it’s not true in today’s math, invent a new system in which it is.
Proof by authority: “Well, Don Knuth says it’s true, so it must be!”
Proof by intuition: “I have this gut feeling.”

http://jwilson.coe.uga.edu/EMT668/EMAT6680.F99/Challen/proof/proof.html

As a mathematician you would find this funny… Only if all math are like this…

http://en.wikipedia.org/wiki/Invalid_proof

Some of these were pretty funny too…

 
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Another I’ve heard of is “Proof by vigorous hand-waving” but I did chuckle quietly when I read this post =]

Nice find.

 
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Proof by Marh: “I got a B, so it’s probably right”.

 
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I remember one similar to

Proof by lost reference: “I know I saw it somewhere….”

that we had in a lecture:

Proof by unobtainable reference: “As shown in the Lithuanian Mathematics Journal of Spring 1957…”

I like proof by obviousness / clarity too, tried to use that in some assignments :)

 
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There’s an anecdote at my uni (and probably every other uni too) about a lecturer who wrote up a Theorem, then “The proof is trivial”. Then he said “Wait a second, IS it trivial?” Left the lecture theatre to think about it and half an hour later returned and exclaimed “Yes, it is definitely trivial!” and continued the lecture. Lol.

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

I have taken calculus. Therefore, I can’t use this proof anymore.

Shit, that was my entire math career.

 
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Proof by profanity: (example omitted)

Proof by divine word: “…And the Lord said, ‘Let it be true,’ and it was true.”

Proof by definition: “We define it to be true.”

My favorites.