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# P I To 31 Trillion Digits......

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https://www.bbc.co.uk/news/technology-47524760

One thing that has always puzzled me, what is the calculation that they do to yield this number? We know it's irrational so there must be some sort of division sum they do that yields a non recurring quotient. Anyone?

One thing that has always puzzled me, what is the calculation that they do to yield this number? We know it's irrational so there must be some sort of division sum they do that yields a non recurring quotient. Anyone?

# Answers

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For more on marking an answer as the "Best Answer", please visit our FAQ.I just checked quickly, and by my reckoning if you take the sum up to n=1000 you get a value pi = 3.1406, and n=10000 still only gets you to 3.1415. So yes, very slow. My pitiful laptop took 4.5 minutes to go to n = 1 million, and that got my only one more digit.

I think the one currently used is the Chudnovsky algorithm, which looks arbitrary to me to but is apparently not -- but is anyway much, much faster than my sum over inverse squares.

e^iπ + 1 = 0.

That's even more mind stretching than pi since it relates two important irrational numbers (Pi - roughly 3.142- and e- roughly 2.718) and an imaginary number (square root of -1)

When I retire I'll see whether I can rearrange it (maybe using the known series for pi and e) and work out the value of i. Simpler than resolving Brexit i reckon

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