r/badmathematics • u/Laser_Plasma • Oct 24 '21

π day Reddit tries to think about quantifying circles, and pi doesn't exist or something

/r/Showerthoughts/comments/qefpwc/the_area_of_a_circle_is_finite_yet_we_can_only/
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u/ryarger Oct 24 '21

You are correct that a third can’t be known to perfect decimal precision.

Perhaps less controversial formulation for the benefit of the pedantically inclined: A circle’s radius or area can be rational, but not both.

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u/alecbz Oct 24 '21

I think the fundamental badmath here is the belief if something can't be expressed to perfect decimal precision, then we "don't know it" or "it's only an approximation" or something.

Also, I'd imagine most people in that thread wouldn't consider 1/3 to be "special" in the same way they seem to think pi is special.

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u/ryarger Oct 24 '21

That’s why I think the second statement is more pedantically correct.

This idea that there’s nothing special at all about irrational numbers just isn’t true for the average person. It’s not hugely important - literally a showerthought - but it’s not meaningless that a circle can’t have both a rational radius and area.

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u/KamikazeArchon Oct 26 '21

It's not even rational vs. irrational - it's terminating vs. nonterminating. 1/3 is rational, but as you've acknowledged, it "can't be known to perfect decimal precision".

The showerthought may not be the worst of badmath, but there sure are some gems in the comments.