reserve i, n for Nat,
  x, y, a for Real,
  v for Element of n-tuples_on REAL,
  p, p1, p2, p3, q, q1, q2 for Point of TOP-REAL n;

theorem
  |.p.|=0 iff p = 0.TOP-REAL n
by Th37,TOPRNS_1:24;
