reserve a,b,c for boolean object;
reserve p,q,r,s,A,B,C for Element of LTLB_WFF,
        F,G,X,Y for Subset of LTLB_WFF,
        i,j,k,n for Element of NAT,
        f,f1,f2,g for FinSequence of LTLB_WFF;
reserve M for LTLModel;

theorem Th6:
  (SAT M).[n,TVERUM]=1
 proof
  assume not(SAT M).[n,TVERUM]=1;
  then not(SAT M).[n,TFALSUM]=0 by Th5;
  hence contradiction by Def11;
 end;
