Logic as a tool a guide to formal logical reasoning ( PDFDrive ) 305

281 Answers and Solutions to Selected Exercises ¬p → (¬q ∨ r) : T , q → ¬r : T , q → p : F q : T, p : F ơr : T q:F ì r:F ơp : F p:T ì ơq r : T ơq : T r:T × q:F × The rule is sound, hence the argument is correct Section 2.4 2.4.2 Introduction rule Elimination rules [A] [B ] B A (↔ I ) A↔B (↔ E ) 2.4.3 (c) [¬¬p]2 A, [¬p]1 ¬p ⊥ p ¬¬p → p A↔B , B B, A↔B A