reserve a,b,c,x,y,z for object,X,Y,Z for set,
  n for Nat,
  i,j for Integer,
  r,r1,r2,r3,s for Real,
  c1,c2 for Complex,
  p for Point of TOP-REAL n;

theorem Th14:
  for f being complex-valued Function holds
  f <> 0*n implies -f <> 0*n
  proof
    let f be complex-valued Function;
    assume
A1: f <> 0*n;
    assume -f = 0*n;
    then --f = -(0*n);
    hence thesis by A1,Th13;
  end;
