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 Th55:
  Sphere(x,r) c= cl_Ball(x,r)
proof
  now
    let y;
    assume y in Sphere(x,r);
    then ||.x - y.|| = r by Th51;
    hence y in cl_Ball(x,r);
  end;
  hence thesis by SUBSET_1:2;
end;
