Logical Proofs, Need help desperately!
Logical Proofs, Need help desperately!
Any help is appreciated.. here is what im dealing with
I am writing everything as it appears on the worksheet
1.~XvY
2.~F
3. D (horseshoe) X
4.~Y&F
/~D&F
1.K (horseshoe) C
2. K&G
3. C (horseshoe) ~F
4. ~D
5. ~F (horseshoe) D
/~Kv~R
I am writing everything as it appears on the worksheet
1.~XvY
2.~F
3. D (horseshoe) X
4.~Y&F
/~D&F
1.K (horseshoe) C
2. K&G
3. C (horseshoe) ~F
4. ~D
5. ~F (horseshoe) D
/~Kv~R
 Arising_uk
 Posts: 11151
 Joined: Wed Oct 17, 2007 2:31 am
Re: Logical Proofs, Need help desperately!
By (horseshoe) do you mean set union U?
If so I'm surprised to find this in predicate logic. Could you give a bit of context to where these proofs are coming from?
If so I'm surprised to find this in predicate logic. Could you give a bit of context to where these proofs are coming from?
Re: Logical Proofs, Need help desperately!
When people say "horseshoe" they usually mean horseshoe but you can't take anything for granted round here.Arising_uk wrote:By (horseshoe) do you mean set union U?
 Arising_uk
 Posts: 11151
 Joined: Wed Oct 17, 2007 2:31 am
Re: Logical Proofs, Need help desperately!
I was wondering if it was just the Logic teacher showing that any symbol can be used to express some kind of logical operator or relation.

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Re: Logical Proofs, Need help desperately!
Mr. Ed used horseshoe logic...
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Re: Logical Proofs, Need help desperately!
This is sentential logic.
Some suggestion:
1.~XvY
2.~F
3. D (horseshoe) X
4.~Y&F

5. ~Y conj. elim. 4.
6. F conj. elim. 4.
7. ~XvY reiteration 1.
8.  ~X

9.  ~X
10.  Y

11.  ~X
12. ~X disj. elim. 7.11.
13. ~D modus tollens 3., 12.

/~D&F conj introd. 6., 13.
Here is your "horseshoe": ⊃ from http://lukasfolsneslea.tripod.com/HTMLLNcharsym1.html.
The logic book your looking for is The Logic Book 5th ed. or so by M. Bergmann, J. Moor and J. Nelson.
Some suggestion:
1.~XvY
2.~F
3. D (horseshoe) X
4.~Y&F

5. ~Y conj. elim. 4.
6. F conj. elim. 4.
7. ~XvY reiteration 1.
8.  ~X

9.  ~X
10.  Y

11.  ~X
12. ~X disj. elim. 7.11.
13. ~D modus tollens 3., 12.

/~D&F conj introd. 6., 13.
Here is your "horseshoe": ⊃ from http://lukasfolsneslea.tripod.com/HTMLLNcharsym1.html.
The logic book your looking for is The Logic Book 5th ed. or so by M. Bergmann, J. Moor and J. Nelson.
 Arising_uk
 Posts: 11151
 Joined: Wed Oct 17, 2007 2:31 am
Re: Logical Proofs, Need help desperately!
Oh! Now I get it, the material conditional, doh!
He could have said 'right horseshoe' or 'left horseshoe' for a better clue.
He could have said 'right horseshoe' or 'left horseshoe' for a better clue.
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