reserve a,a1,a2,v,v1,v2,x for object;
reserve V,A for set;
reserve m,n for Nat;
reserve S,S1,S2 for FinSequence;

theorem Th11:
  A c= Union FNDSC(V,A)
  proof
    set F = FNDSC(V,A);
A1: A = F.0 by Def3;
    dom F = NAT by Def3;
    then F.0 in rng F by FUNCT_1:def 3;
    hence thesis by A1,ZFMISC_1:74;
  end;
