# Ass2 Qu2 (1.1)

Posted by VeerVortexus
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 Ass2 Qu2 (1.1) May 30, 2006 04:08PM IP/Host: ---.saix.net Registered: 13 years ago Posts: 6 Rating: 0
Hello All.

i break the disjuncts of B v C up, but when i do the subproofs for B, i can only prove A/\B for that subproof, and when i do the subproof for C i only prove A/\C. How do i prove A/\C for subproof B and A/\B for subproof C.What am i missing?

After all you have to prove (A/\ for disjuncts B and C, and also have to prove (A/\C) for disjuncts B and C.

Thanks for the help.

 Re: Ass2 Qu2 (1.1) May 30, 2006 06:08PM IP/Host: ---.saix.net Registered: 13 years ago Posts: 6 Rating: 0
I still dont understand.If i have proved A/ \B in subproof B, then youre saying i should use V Intro, but thats not possible, because i have only proved one half of that subproof.I still need to show that i can derive A/\C from it as well, even when i prove in subproof C that A/ \C, thats only one half of the other half.

In other word to perform V Intro, i would have to prove that

C---> A/ \B i must still prove thsi to be allowed to perfrm v Intr
C---> A/ \C i get this part
B---> A/ \B i get this part
B---> A/ \C i must still prove this to be allowed to perfrm v Intr

Proof by cases as above.

So that both disjuncts derive the same conclusion in each instances.

Am i understanding this.

Thank you.
 Re: Ass2 Qu2 (1.1) May 30, 2006 06:19PM IP/Host: ---.saix.net Registered: 13 years ago Posts: 6 Rating: 0
PLEASE FORGIVE ME!!I have just worked it out.My goodness, it was so simple an i know it was, but i was delving so deeply into the rules, that i missed the whole simplicity of it all.Sorry, im a real dumbo at times.Thanks for the hint, i saw it immediately after the above post was sent, so please ignore that post.

Much appreciated for the help, and sorry if i wasted your time.

Veer
 Re: Ass2 Qu2 (1.1) May 30, 2006 09:55PM IP/Host: ---.cg.shawcable.net Registered: 13 years ago Posts: 43 Rating: 0
No problem and no time wasted.
This module is not not easy and sometimes a little help goes a long way to make things clearer.

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