理則學 練習20 範例 (取自梅子姐)
2008/03/15 20:25
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A-1
5 | |
1. –(∃x)Hx | Premise |
2. –[–(x)Hx] | Premise |
3. (x)–Hx | From 1 by Q.E. |
4. –Ha | From 3 by U.I. |
5. (x)Hx | From 2 by Double negation. |
6. Ha | From 5 by U.I. |
7. Ha&–Ha | From 6, 4 by adjunction |
C-3 (x)Gx ; (∃x)–Gx
1. (x)Gx | Premise |
2. (∃x)–Gx | Premise |
3. –Ga | From 2 by E.I. |
4. Ga | From 1 by U.I. |
5. Ga&–Ga | From 4, 3 by adjunction |
