You can't or won't because it shows that your clever little nit picking point is essentially irrelevant, and you know it.
Not really - you constantly claim the moral and intellectual high ground yet when holes in your arguments are exposed, you dismiss them as irrelevant as an excuse for not realising they were there in the first place.
The complete irrelevance is this ultimate coning angle - do the blades cone up as Nr decreases? Yes we all know that.
Is there an ultimate angle beyond which they won't go because of some special mathematical relationship that only you understand? I don't think so.
You are forgetting the practical when dealing with the theoretical - different rotor designs will have different physical limits to their coning - the blades themselves in a teetering head, the physical limits of the hinges in an articulated head, and the limits of deformation in the elastomeric hinges in a semi-rigid head (titanium star bending on a Lynx).
So why postulate that there is an ultimate coning angle? Do designers use it? No. Could or would pilots use it? No. Do engineers consider it? No.
So therefore, on the subject of irrelevance - where does your rather muddled argument and proposed theory stand????