contradiction truth tree

Asked Nov 07 '16 at 15:16

Active Nov 07 '16 at 15:25

Viewed 153 times

To get straight to the point: I have to prove, using a truth-tree, that the following set of propositions (image 2) is contradictory. You can see the way I proceeded in image 3 and the way the exemple is solved in the book in image 1.

At one point I have started "decomposing" proposition no.3 and the book proposition no.2 - which lead us to a different order of tree-branches and a different ending (mine does not end in a contradiction, if I the problem correctly).

I guess somewhere I went wrong, or I didn't follow through or I just simply don't get something - if anyone can help it would I would be really thankful!

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edited Nov 07 '16 at 15:25

JMP

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asked Nov 07 '16 at 15:16

SmallAxe

Where comes from the branch $s$ and $\lnot q$ ? – Mauro ALLEGRANZA Nov 07 '16 at 15:29
Assuming you have used correctly the rules, $s$ in 2) close with $\lnot s$ in 6). – Mauro ALLEGRANZA Nov 07 '16 at 15:56

contradiction truth tree

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