reserve i,j,n,k,m for Nat,
     a,b,x,y,z for object,
     F,G for FinSequence-yielding FinSequence,
     f,g,p,q for FinSequence,
     X,Y for set,
     D for non empty set;

theorem Th59:
  (App {}).{} = {}
proof
  reconsider E={} as FinSequence;
  E in doms {} by Th46,TARSKI:def 1;
  then len ((App {}).E)=len E by Def9;
  hence thesis;
end;
