A statement is true if the denial of the consequent is inconsistent with the premises.If the statement is true there must exist a derivation for it.Inverting the semantic tableuax gives the inference rules,is there any other method which one can use?
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You can form the contrapositive statement and then prove that one by contradiction. =) – Michael Mar 02 '21 at 17:44
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thanks will look into it – Mar 02 '21 at 17:45
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2@Michael While every proof by contraposition can be recast as a proof by contradiction, the converse is not necessarily true. – ryang Mar 02 '21 at 17:58
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https://math.stackexchange.com/questions/243770/can-every-proof-by-contradiction-also-be-shown-without-contradiction – ℋolo Mar 02 '21 at 23:45