Answer to Question #270674 in Discrete Mathematics for V.kathiravan

Question

What and Define Tautology and contradiction

Answer 1

A formula of propositional logic is a tautology if the formula itself is always true, regardless of which valuation is used for the propositional variables. For example, $A \lor \lnot A$.

A formula of propositional logic is a contradiction if the formula itself is conflict with itself. For example, $A \land \lnot A$.