razvan jigorea & friends: the blog

HOW TO PROVE IT, PART 1

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 intimidation:

‘Trivial’.

proof by vigorous handwaving:

Works well in a classroom or seminar setting.

HOW TO PROVE IT, PART 2

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 omission:

‘The reader may easily supply the details’
‘The other 253 cases are analogous’
‘…’

HOW TO PROVE IT, PART 3

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 funding:

How could three different government agencies be wrong?

proof by eminent authority:

‘I saw Karp in the elevator and he said it was probably NP-
complete.’

HOW TO PROVE IT, PART 4

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.

HOW TO PROVE IT, PART 5

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.

HOW TO PROVE IT, PART 6

proof by picture:

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

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.

HOW TO PROVE IT, PART 7

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 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.

(Thanks, steju)

Poate totuşi am făcut o mare greşeală întorcîndu-mă din Suedia: acolo miniştrii demisionează pentru că nu şi-au plătit taxa TV.

Nice advertisement is hard to come by.

Newspaper bullshit, payed up “studies” and polls are all alright but not an individual expressing his (maybe objectively incorrect) opinion.

about:predius: Mentioning a certain word per programing language and license.

In toamna lui ‘96 s-a votat schimbarea. Ce s-a schimbat in ultimii zece ani. Sau nu.

Un domn, numit Thierry F. a scris o carte despre cum se poate trăi fără muncă. Citiţi şi vedeţi, la 23€ pe lună chiria, poate că nu-i aşa de greu.

Ion Iliescu - carmaciul Securitatii de la Iasi, A avizat actiuni de politie politica, da’ e un om cinstit, si sarac, iar gura nu-i miroase.

Edit: Cum să-i miroasă gura, săracul de el, dacă usturoi n-a păpat? Silly me!

Festivalul filmului olandez in Timisoara, 9-11 octombrie.

(Thanks, Andra.)

…can get both your iPod (literally) and yourself (metaphorically) in deep shit.