reserve A for QC-alphabet;
reserve sq for FinSequence,
  x,y,z for bound_QC-variable of A,
  p,q,p1,p2,q1 for Element of QC-WFF(A);
reserve s,t for bound_QC-variable of A;
reserve F,G,H,H1 for Element of QC-WFF(A);
reserve x,y,z for bound_QC-variable of A,
  k,n,m for Nat,
  P for ( QC-pred_symbol of k, A),
  V for QC-variable_list of k, A;

theorem Th49:
  H is conjunctive implies (F is_immediate_constituent_of H iff F
  = the_left_argument_of H or F = the_right_argument_of H)
proof
  assume H is conjunctive;
  then H = (the_left_argument_of H)'&' the_right_argument_of H by Th3;
  hence thesis by Th45;
end;
