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December 31, 2015 01:18
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| P1: A => B ^ C | |
| P2: B => ¬D | |
| P3: C => D | |
| P4: (added by Proof by Contradiction) A | |
| Conclusion: false (proof by contradiction) | |
| Assertion Justification | |
| ------------------------------ | |
| A P4 | |
| A => B ^ C P1 | |
| B ^ C 1, 2, modus ponens | |
| B 3, simplification | |
| B => ¬D P2 | |
| ¬D 4, 5, modus ponens | |
| C 3, simplification | |
| C => D P3 | |
| D 7, 8, modus ponens | |
| D ^ ¬D 6, 9, addition | |
| false 10, rewrite, QED |
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