My Little Logic Problem...
| Good [+1]Toggle ReplyLink» basdini replied on Thu Jan 22, 2009 @ 11:39pm |
 Coolness: 145340 | I need to prove (p -> q)->(~~p->~~q) from the empty set.
i'm only allowed to use These three axioms: p->(q->p) [PL1] (p->(q->r))->((p->q)->(p->r)) [PL2] (~p->~q)->(q->p) [PL3] These four theorems ~p->(p->q) [pt1] p->p [pt2] ~~p->p [pt3] p->~~p [pt4] remember, any uniform substitution instance of an axiom or theorem yield an axiom or theorem, any suggestions, serious answers only |
| I'm feeling surly right now.. | |
| Good [+1]Toggle ReplyLink» flo replied on Fri Jan 23, 2009 @ 12:55pm |
 Coolness: 146465 | In which deduction system are you ? According to the axioms, it looks like you're in Hilbert's propositional calculus... but it doesn't say which inference rules you're allowed to use.
If you only have the modus ponens, then the proof will be very tiresome (and I won't take the time nor the energy to write it... I've never really liked propositional logic)... Do you also have the deduction theorem ? Or any other inference rule ? It would be much easier with more rules :) |
| I'm feeling phd powa !!! right now.. | |
| Good [+1]Toggle ReplyLink» rawali replied on Fri Jan 23, 2009 @ 1:04pm |
 Coolness: 140825 | |
| I'm feeling lovely right now.. | |
| Good [+1]Toggle ReplyLink» flo replied on Fri Jan 23, 2009 @ 1:09pm |
| Coolness: 146465 | you don't wanna know what we're discussing here... i tell you :P |
| I'm feeling phd powa !!! right now.. | |
| Good [+1]Toggle ReplyLink» rawali replied on Fri Jan 23, 2009 @ 1:11pm |
| Coolness: 140825 | |
| I'm feeling lovely right now.. | |
| Good [+1]Toggle ReplyLink» JasonBeastly replied on Fri Jan 23, 2009 @ 1:14pm |
 Coolness: 76850 | Ow. Brain. Melt. |
| I'm feeling gwan bottirass right now.. | |
| Good [+1]Toggle ReplyLink» flo replied on Fri Jan 23, 2009 @ 1:14pm |
| Coolness: 146465 | Originally Posted By RAWALI
why the hell did the pic show up in a white box... and all small... because you put "video" tags instead of "img" tags ;) |
| I'm feeling phd powa !!! right now.. | |
| Good [+1]Toggle ReplyLink» rawali replied on Fri Jan 23, 2009 @ 1:27pm |
| Coolness: 140825 | true... my mistake |
| I'm feeling lovely right now.. | |
| Good [+1]Toggle ReplyLink» Strik_IX replied on Fri Jan 23, 2009 @ 1:35pm |
 Coolness: 88780 |  |
| I'm feeling <( ^_^ )> right now.. | |
| Good [+1]Toggle ReplyLink» Gamos replied on Fri Jan 23, 2009 @ 1:37pm |
 Coolness: 93635 | yeah |
| I'm feeling like a failure right now.. | |
| Good [+1]Toggle ReplyLink» v.2-1 replied on Fri Jan 23, 2009 @ 3:53pm |
 Coolness: 159260 |  |
| I'm feeling like marcus phenix right now.. | |
| Good [+1]Toggle ReplyLink» rawali replied on Fri Jan 23, 2009 @ 3:58pm |
| Coolness: 140825 | whut aint no country I ever heard of! they speak english in whut? |
| I'm feeling lovely right now.. | |
| Good [+1]Toggle ReplyLink» Screwhead replied on Fri Jan 23, 2009 @ 4:02pm |
 Coolness: 685730 | Say whut again! I dare you! |
| I'm feeling your norks right now.. | |
| Good [+1]Toggle ReplyLink» v.2-1 replied on Fri Jan 23, 2009 @ 4:05pm |
| Coolness: 159260 | Say WHAT again one goddam time. I dare you. I double dare you. |
| I'm feeling like marcus phenix right now.. | |
| Good [+1]Toggle ReplyLink» rawali replied on Fri Jan 23, 2009 @ 5:00pm |
| Coolness: 140825 | Originally Posted By V.2.0.MINUS.1
Say WHUT again one goddam time. I dare you. I double dare you motherfucka! double fixed |
| I'm feeling lovely right now.. | |
| Good [+1]Toggle ReplyLink» basdini replied on Sat Jan 24, 2009 @ 12:29am |
| Coolness: 145340 | when i first saw the thread reply counter i was all like "wow people were really interested in this", then i opened it...
anyways, to answer you flo, i'm allowed to use modus ponens and [DT] (deductive theorem) but not [SPE] (subsitutable proved equivalence) |
| I'm feeling surly right now.. | |
| Good [+1]Toggle ReplyLink» rawali replied on Sat Jan 24, 2009 @ 4:47am |
| Coolness: 140825 | honnestly... if i had any idea what you guys were talking about im sure id be crazy involved and intrested... but even my two cegep math classes are in no way helping me understand anything here |
| I'm feeling lovely right now.. | |
| Good [+1]Toggle ReplyLink» Screwhead replied on Sat Jan 24, 2009 @ 7:39am |
| Coolness: 685730 |  |
| I'm feeling your norks right now.. | |
| Good [+1]Toggle ReplyLink» flo replied on Sat Jan 24, 2009 @ 8:08am |
| Coolness: 146465 | lol
Originally Posted By BASDINI
anyways, to answer you flo, i'm allowed to use modus ponens and [DT] (deductive theorem) but not [SPE] (subsitutable proved equivalence) hehe sorry but I guess you'll have to do it by yourself... it's the kind of exercise one can only bear to do once in his life :P Good luck, though, you will need several trial-and-errors before having found the 10 or 20 steps of this proof. Here's a little piece of advice : since it's not easy to see the substitutions and keep them in mind, try to write down the actual contents of each substitution each time ; e.g. when you apply MP, write both {A, A->B} |- B and, say, {p, (p->(q->p))} |- (q->p), or at least {p, axiom_1} |- (q->p) ... otherwise you probably won't go anywhere, even with a large brain ;) |
| I'm feeling phd powa !!! right now.. | |
| Good [+1]Toggle ReplyLink» basdini replied on Sat Jan 24, 2009 @ 3:12pm |
| Coolness: 145340 | i don't even have to do it, but my teacher is offering to buy beer after class for the person who gets it, i don't even want the beer, i just want to show up this twerp in my class... |
| I'm feeling surly right now.. | |
My Little Logic Problem...
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