(p→q)→r, s→¬p , t , (¬s∧t) → q ⊢ r Any help would be appreciated
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Start with $t$ and assume either $s$ or $\neg s$. Can both cases lead to $r$? – Graham Kemp Oct 11 '16 at 13:19
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Yes. For that we can use LEM rule.(sV¬s) – miss_b. Oct 11 '16 at 13:43
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Assume $P$, derive $Q$. Then discharge the assumption $P$ obtaining $P \implies Q$. Use modus ponens to derive $R$ from premise 1. – Frank Hubeny Feb 19 '19 at 02:54
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You can start with ¬r, and find the contradiction (t∧¬t). It took me 14 steps. Maybe it is not the best way, but reductio ad absurdum usually works fine :)
Heraclitus
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