Timeline for Reductio ad absurdum or the contrapositive?
Current License: CC BY-SA 4.0
17 events
| when toggle format | what | by | license | comment | |
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| Mar 18, 2021 at 10:03 | history | edited | Aryeh Kontorovich | CC BY-SA 4.0 |
deleted 1 character in body
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| Dec 11, 2017 at 22:15 | comment | added | Andrej Bauer | Ah, classical mathematicians finding reasons for intuitionistic proofs. | |
| Dec 11, 2017 at 18:40 | history | edited | Joel David Hamkins | CC BY-SA 3.0 |
fixed typo (after all these years)
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| Sep 19, 2012 at 3:53 | comment | added | Sridhar Ramesh | ("If a proof if" should be "If a proof of", of course. I am too lazy to delete the comment and retype the whole thing just to fix it) | |
| Sep 19, 2012 at 3:51 | comment | added | Sridhar Ramesh | If a proof if $p$ implies $q$ by contrapositive (establishing $\neg q$ implies $\neg p$) is useful because one learns intermediately that ($\neg r_1$ implies $q$), ($\neg r_2$ implies $q$), etc., then a proof of $p$ implies $q$ by contradiction (establishing $\neg (p \wedge \neg q)$) is useful because one learns intermediately ($p \wedge \neg r_1$ implies $q$), ($p \wedge \neg r_2$ implies $q$), etc. | |
| Oct 31, 2010 at 23:52 | comment | added | Pietro Majer | Indeed Euclid's original proof is not by contradiction, but consists in the direct construction. | |
| Oct 20, 2010 at 20:27 | history | edited | gowers | CC BY-SA 2.5 |
Corrected two spelling mistakes
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| Feb 9, 2010 at 15:19 | comment | added | Matthew Daws | An interesting corollary of this is that, if you are making a first attempt at proving something, then proof by contradication can be very profitable, precisely because you don't end up worrying about all the intermediate implications. Of course, if you are successful, you should then check to see if there is a better proof... | |
| Jan 20, 2010 at 15:38 | history | edited | Joel David Hamkins | CC BY-SA 2.5 |
Added example about infinity of primes
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| Jan 20, 2010 at 13:26 | history | edited | Joel David Hamkins | CC BY-SA 2.5 |
fixed typo
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| Jan 20, 2010 at 10:44 | comment | added | Joel David Hamkins | Oh, Thanks for accepting! It looks like I wasn't too late after all. | |
| Jan 20, 2010 at 10:40 | history | edited | Joel David Hamkins | CC BY-SA 2.5 |
improved formatting
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| Jan 20, 2010 at 10:31 | history | edited | Joel David Hamkins | CC BY-SA 2.5 |
improved formatting
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| Jan 20, 2010 at 10:03 | vote | accept | Harry Gindi | ||
| Jan 20, 2010 at 9:59 | comment | added | Joel David Hamkins | Thanks, Harry. I appreciate it. It looks like I was late to this party... | |
| Jan 20, 2010 at 9:51 | comment | added | Harry Gindi | I was wondering when you'd come by. You usually have really good answers to these kinds of questions. | |
| Jan 20, 2010 at 9:37 | history | answered | Joel David Hamkins | CC BY-SA 2.5 |