For some reason, this reminds me of oyasumi punpun.

Oyasumi Homura.

who even calls something lim x->pi/2 tan(x). Besides, its not like it necessarily diverges to infinity (or even better: converges to infinity, not sure whats "uneigentliche konvergenz" jn english). It may as well tend to -infinity or have no value at all.

It may as well tend to -infinity or have no value at all.

Which is why we say it doesn't exist. I think the doujin author had that in mind. Also that it depends which side you look at it from.