theorem Th60:
  for V being RealLinearSpace, v being VECTOR of V holds Sum<* v,v *> = 2 * v
proof
  let V be RealLinearSpace, v be VECTOR of V;
  thus Sum<* v,v *> = v + v by Th45
    .= 1 * v + v by Def8
    .= 1 * v + 1 * v by Def8
    .= (1 + 1) * v by Def6
    .= 2 * v;
end;
