Divide by zero error! A division by zero is undefined, so I think
John's statement is correct. Even if you take the limit as the
effective speed goes to zero, the result is infinity, which is also,
theoretically, an undefineable number since it leads to inherent
contradictions in the strict sense. If we were to take ANM as a strict
mathematical concept, then I fear we would be laughed at. But
practically speaking, you're never going to have an effective ground
speed of 0 in an airplane.