reserve i for Nat,
  j for Element of NAT,
  X,Y,x,y,z for set;
reserve C for initialized ConstructorSignature,
  s for SortSymbol of C,
  o for OperSymbol of C,
  c for constructor OperSymbol of C;
reserve a,b for expression of C, an_Adj C;
reserve t, t1,t2 for expression of C, a_Type C;
reserve p for FinSequence of QuasiTerms C;
reserve e for expression of C;
reserve a,a9 for expression of C, an_Adj C;
reserve q for pure expression of C, a_Type C,
  A for finite Subset of QuasiAdjs C;
reserve T for quasi-type of C;

theorem Th106:
  variables_in (({}QuasiAdjs C) ast q) = variables_in q
proof
  set A = {}QuasiAdjs C;
  set AA = {variables_in a where a is quasi-adjective of C: a in A};
  AA c= {}
  proof
    let x be object;
    assume x in AA;
    then ex a being quasi-adjective of C st x = variables_in a & a in A;
    hence thesis;
  end;
  then
A1: AA = {};
  variables_in (A ast q) = (union AA) \/ (variables_in q) by Th104;
  hence thesis by A1,ZFMISC_1:2;
end;
