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