wtf!

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Saved to my thinkbank.

I understand the formula but not the implications, other than determining whether a given number is rational 😅

The case when x is rational is easier to see as m!x will be an integer from some value of m.

Cool formula 🤓

The other side, I guess the cos^2 is less than 1 so the limit is 0.

I choose many server to save my images

I can live with it.

I mean … yeah …

Can x at least be reasonable?

ITS ALL GREEK TO ME :)

If X is rational, there will be at least one (actually, infinitely many) Ms for which MX is an integer, and therefore the cosine is either -1 or +1

M! includes many even numbers, therefore the cosine will be +1, not -1

For irrational X, the cosine is always strictly between -1 and +1, and therefore tends to zero as n increases

(I still suspect in missing something, no pen and paper at hand)

And now I'm curious about complex X too

The reason it cannot take a value of -1 is simply because its an even power of cos(x).

I've subsequently realised that you almost certainly knew the power was even and hence it takes a value of 1 in any case. Apologies!