Timeline for Help with a proof for the following arguments
Current License: CC BY-SA 3.0
14 events
| when toggle format | what | by | license | comment | |
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| Oct 30, 2014 at 4:20 | comment | added | cookie monster | I marked your answer for providing more details however I'm not familiar with some of the rules you used so I followed your answer as a guide to come up with similar solution. I end up opening a new one here to avoid complicating this thread. Please take a look at it and confirm if my steps are valid. I am having problems discharging an assumption, so your help will be appreciated. | |
| Oct 30, 2014 at 4:17 | vote | accept | cookie monster | ||
| Oct 29, 2014 at 20:26 | history | edited | Mauro ALLEGRANZA | CC BY-SA 3.0 |
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| Oct 29, 2014 at 18:03 | comment | added | cookie monster | I think you also made a mistake with step 13, you got it with -I not →I | |
| Oct 29, 2014 at 16:35 | comment | added | Mauro ALLEGRANZA | @cookiemonster - in 12 the symbol ⊥ stay for a contradiction : step 4) ¬ C and step 11) C ; thus, having derived a contradiction, we negate the assumption 5) A & B, getting 13) ¬ (A & B). This can be done with the abbreviation ¬ P := P → ⊥; in this way, deriving a contradiction from ¬ C, C is nothing else than apply →E to C → ⊥, C in order to derive ⊥. Then, having (A & B) ⊢ ⊥, we derive (A & B) → ⊥, i.e. ¬ (A & B) by →I. | |
| Oct 29, 2014 at 16:34 | comment | added | cookie monster | please can you go over your answer again and correct the rest! | |
| Oct 29, 2014 at 16:28 | comment | added | Mauro ALLEGRANZA | @cookiemonster - right, tanks ! coorected the typo into steps 6 and 8. For step 7, it is correct : A ⊢ B → A, for every A, because A → (B → A) is valid (it is a tautology). | |
| Oct 29, 2014 at 16:28 | comment | added | cookie monster | Also you can't really get step 10 unless you have (A → B) ^ (B → A). I don't understand what you mean by step 12. Step 13 is not clear as well. I'm not sure if I can understand this well, it seems like you are using the symbols in a different way. | |
| Oct 29, 2014 at 16:26 | history | edited | Mauro ALLEGRANZA | CC BY-SA 3.0 |
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| Oct 29, 2014 at 16:10 | comment | added | cookie monster | Isn't step 6 from ^ E on line 5? Also step 7 doesn't seem correct.You don't even have B yet? In addition on step 8, shouldn't that be ^ E on line 5? | |
| Oct 29, 2014 at 14:37 | history | edited | Mauro ALLEGRANZA | CC BY-SA 3.0 |
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| Oct 29, 2014 at 11:24 | history | edited | Mauro ALLEGRANZA | CC BY-SA 3.0 |
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| Oct 29, 2014 at 9:02 | history | edited | Mauro ALLEGRANZA | CC BY-SA 3.0 |
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| Oct 29, 2014 at 8:44 | history | answered | Mauro ALLEGRANZA | CC BY-SA 3.0 |