reserve X for ComplexUnitarySpace;
reserve x, y, w, g, g1, g2 for Point of X;
reserve z for Complex;
reserve p, q, r, M, M1, M2 for Real;
reserve seq, seq1, seq2, seq3 for sequence of X;
reserve k,n,m for Nat;
reserve Nseq for increasing sequence of NAT;

theorem Th50:
  y in Ball(x,r) implies y in cl_Ball(x,r)
proof
  assume y in Ball(x,r);
  then ||.x - y.|| <= r by Th40;
  hence thesis;
end;
