Completeness emma Let p be a noncontradictory path of a finished tableau T Define a truth assignment A on all propositional letters A as follows O A(A)=Tif TA is an entry on P O A(A=Otherwise If v is the unique valuation extending the truth assignment A. then y agrees with all entries of PCompleteness . Lemma . . Let P be a noncontradictory path of a finished tableau τ . Define a truth assignment A on all propositional letters A as follows: 1. A(A) = T if TA is an entry on P. 2. A(A) = F otherwise. If V is the unique valuation extending the truth assignment A, then V agrees with all entries of P. Yi Li (Fudan University) Discrete Mathematics April 16, 2013 12 / 17