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Assignment 2 Question2 part 1.2

Posted by ToKnowOrNotToKnow 
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Assignment 2 Question2 part 1.2
May 26, 2006 04:30AM
Can anyone give me a hint how to get !B ?

confused smiley
avatar Re: Assignment 2 Question2 part 1.2
May 26, 2006 03:20PM
The only way I know of that can give you ¬B is to use negation introduction. If you can't follow this year's textbook, go back to the textbook from COS161 (Gutenplan), it's expained much better there.

Negation introduction (reductio ad absurdum) basically relies on you to assert something. If that assertion causes a contradiction somewhere down the line, your original assertion must be false, and the negation of your assertion therefore must be true.
Re: Assignment 2 Question2 part 1.2
May 30, 2006 05:02AM
THANKS robanaurochs

What I'm trying to do is to get to A <-> !B by proving
A -> !B and !B -> A

Now I got the part from A -> !B but are having difficulty to get !B -> A.


As I see it there is noting I can do when trying to prove !B->A as I have to assume !B but that leads to nowhere.



Re: Assignment 2 Question2 part 1.2
May 30, 2006 04:46PM
Did you use VE? on premise 1?
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