13 lines
543 B
Text
13 lines
543 B
Text
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-- Backward chaining with hypotheses
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constants {P Q R S T U : Prop}
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constants (Huq : U → Q) (Hur : U → R) (Hus : U → S) (Hut : U → T)
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attribute Huq [backward]
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attribute Hur [backward]
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attribute Hus [backward]
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attribute Hut [backward]
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definition lemma1 : (P → Q) → P → Q := by blast
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definition lemma2 : (P → Q) → (Q → R) → P → R := by blast
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definition lemma3 : (P → Q) → (Q → R) → (R → S) → P → S := by blast
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definition lemma4 : (P → Q) → (Q → R) → (R → S) → (S → T) → P → T := by blast
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