Propositional Logic When to Use Use this skill when working on propositional-logic problems in mathematical logic. Decision Tree 1. Identify Formula Structure - Classify: tautology, contradiction, or contingent? - Main connective: AND, OR, IMPLIES, NOT, IFF? - to check satisfiability 2. Truth Table Method - For small formulas (<=4 variables): enumerate all valuations - - Tautology = all T, Contradiction = all F 3. Natural Deduction - Apply inference rules: Modus Ponens, Modus Tollens - Conditional proof: assume antecedent, derive consequent - 4. Semantic Tableaux - Build tree by decomposing f…