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Exercise 3.1
1. |
Which of the following sequents is correct? Where the sequent is incorrect, give a counterexample. | |
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(i)
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¬[P®Q] |= [¬P®Q] | |
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(ii)
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¬[P®Q] |= [P®¬Q] | |
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(iii)
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[P®Q] |= ¬[P®¬Q] | |
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(iv)
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[P®Q], [R®Q] |= [[PÚR]®Q] | |
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(v)
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[[P®Q]Ú [R®Q]] |= [[PÚR]®Q] | |
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(vi)
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|= [[P®Q]«[¬P®¬Q]] | |
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(vii)
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|= [[P®Q]«[¬Q®¬P]] | |
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(viii)
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[PÙ¬P] |= Q | |
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(ix)
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Q |= [P®P] | |
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