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What field do you work in, and how many digits of pi do you use? (lemmy.world)

submitted 8 months ago by [email protected] to c/[email protected]

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This article says that NASA uses 15 digits after the decimal point, which I'm counting as 16 in total, since that's how we count significant digits in scientific notation. If you round pi to 3, that's one significant digit, and if you round it to 1, that's zero digits.

I know that 22/7 is an extremely good approximation for pi, since it's written with 3 digits, but is accurate to almost 4 digits. Another good one is √10, which is accurate to a little over 2 digits.

I've heard that 'field engineers' used to use these approximations to save time when doing math by hand. But what field, exactly? Can anyone give examples of fields that use fewer than 16 digits? In the spirit of something like xkcd: Purity, could you rank different sciences by how many digits of pi they require?

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[–] [email protected] 1 points 8 months ago (3 children)

if you round it to 1, that’s zero digits.

Isn’t rounding to zero digits a nonsensical concept? And “1” is one digit, not zero digits.

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[–] [email protected] 1 points 8 months ago* (last edited 8 months ago)

Why would anyone use this fakenass number it makes no sense

[–] [email protected] 1 points 8 months ago (1 children)

Well, I have two answers. If it is mental math I use 3.1 and round up. If I am calculating something I care about I use my TI-86 which has pi to 14 digits.

Practically speaking, I don't often need to convert diameter to circumference but I do occasionally need to calculate area or volume and in those cases I have way more error in other measurements or assumptions (2 or 3 digits) so 5 digits of pi is more than enough.

[–] [email protected] 1 points 8 months ago (1 children)

So you round up 3.1 to 3.2?

[–] [email protected] 1 points 8 months ago

No I round the result to compensate for the error.

[–] [email protected] -2 points 8 months ago

I use 100 trillion digits

[–] [email protected] -2 points 8 months ago

I use 100,000,000,000,000

[–] [email protected] -2 points 8 months ago

I use 100 trillion digits

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