Assignment and valuation merrem Given a truth assignment a there is a unique truth valuation V such that V(a)=A(a) for every propositional letter a roo The proof can be divided into two step O Construct a v from a by induction on the depth of the associated formation tree o Prove the uniqueness of v with the same A by nduction bottom-upAssignment and Valuation . Theorem . . Given a truth assignment A there is a unique truth valuation V such that V(α) = A(α) for every propositonal letter α. . Proof. . . The proof can be divided into two step. 1. Construct a V from A by induction on the depth of the associated formation tree. 2. Prove the uniqueness of V with the same A by induction bottom-up. Yi Li (Fudan University) Discrete Mathematics April 2, 2013 7 / 20