What is Pi?

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14 Mar 2014, 10:47 pm

In light of this day (it's still 3/14 where I am as of this typing), this is what I ask, this eternal Q, "What is Pi?"

Nobody knows what it is. It is a number. It is a nice pastry, too. Or it can be a meat pie, if you live in England or Australia. While I am not a mathingly-inclined person (and I'm Asian, on top of that, so I've dispelled the myth that ALL Asians are good at math pretty much FOREVER), will we, as a species, EVER find out the true meaning of this mystery? I say, who knows, probably, probably not.

This is E2LA wishing you all a happy Stonehenge Day, and may your life be long and unpredictable as Pi.

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ruveyn
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14 Mar 2014, 10:52 pm

Pi is defined for circles on a plane. Pi is the ratio of the circumference of a circle to its diameter.

Yes pi exists. Pi is not a rational number so it cannot be written as a finite or repeating decimal fraction.

Dhp
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16 Mar 2014, 4:10 pm

Pi is also a black and white, independent movie as well. An interesting one at that, but a little gory at times. The above poster is correct; the ancient greeks knew of this number and did not like it, as it is an irrational number. They liked rational numbers. I think the ancient Egyptians knew of it as well, and gave an approximation of 22/7. But me? I like cherry pie! (sings) She's my cherry pie, with a smile on her face 10 miles wide...just kidding. I'm not a fan of Warrant, but that song was so fitting. lol

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19 Mar 2014, 2:35 am

ruveyn wrote:

Pi is defined for circles on a plane. Pi is the ratio of the circumference of a circle to its diameter.

Yes pi exists. Pi is not a rational number so it cannot be written as a finite or repeating decimal fraction.

Listen to this guy -- he is nearly always right.

LupaLuna
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19 Mar 2014, 3:22 am

Perhaps this graphic illustration from Wikipedia might help.

ModusPonens
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22 Mar 2014, 3:57 pm

Well, it's the square root of 6 times the sum of all the squares of the inverses of natural numbers.

Eccles_the_Mighty
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24 Mar 2014, 3:37 pm

It's 3.141592653589793238462643383279502884197169399375105820974944592307816406286 208998628034825342117067982148086513282306647093844609550582231725359408128481 117450284102701938521105559644622948954930381964428810975665933446128475648233 786783165271201909145648566923460348610454326648213393607260249141273724587006 606315588174881520920962829254091715364367892590360011330530548820466521384146 951941511609433057270365759591953092186117381932611793105118548074462379962749 567351885752724891227938183011949129833673362440656643086021394946395224737190 702179860943702770539217176293176752384674818467669405132000568127145263560827 785771342757789609173637178721468440901224953430146549585371050792279689258923 542019956112129021960864034418159813629774771309960518707211349999998372978049 951059731732816096318595024459455346908302642522308253344685035261931188171010 003137838752886587533208381420617177669147303598253490428755468731159562863882..

Why?

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25 Mar 2014, 3:11 pm

Eccles_the_Mighty wrote:

But the only reason why all the extra decimal places would come into play is if you were trying to get a femtometer accurate calculation of area on parsecs of area. --a bit redundant, isn't it?

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26 Mar 2014, 1:25 pm

Pi is not something that occurs to me in every day life. It's too complicated for me. I learnt it in a maths lesson at school once, and all I can remember is it has something to do with the number 3.14.

I like a song about Pi, not so much for the subject, but just the way the tune goes. I have listened to it a lot, although I still can't remember the numbers. http://www.youtube.com/watch?v=AtgfsRH3H3U&hd=1

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26 Mar 2014, 2:46 pm

Joe90 wrote:

As it's infinite it's impossible to know all pi numbers anyway.

Eccles_the_Mighty
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26 Mar 2014, 5:25 pm

OK, why all the digits?

Short answer: Because I can.

Long answer: I have a nasty habit of doing strange things for fun, technical stuff. My Fluke voltmeter measures to 1mV (0.001V) which to me wasn't enough so I spent weeks building a voltmeter that could measure to 0.000001V. When I did my degree I built a calculator for my final year project but rather than use decimal it used Roman numerals, so if you really wanted to work out XVII-V then I was your man. This is more complicated than you think because the Romans didn't have zero but I figured out how to make it work anyway, just for fun. As demonstrated by Cmdr Spock in Star Trek TOS computing Pi is a great stress test for computers so when someone asked what Pi was I downloaded a program in C++, compiled it, and ran it for a while on one of my computers. The result is what you see, Pi to more digits than you will ever need.

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26 Mar 2014, 10:48 pm

Eccles_the_Mighty wrote:

Why not. A basic theorem of Euclid is that all circles are similar so the ratio of the circumference of the diameter is a well defined constant.

It came as a rude shock to the Pythagorians that there are numbers which are not the ratio of two integers. Pi is one of them and the square root of a non-square integer is also one of them.

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27 Mar 2014, 6:33 am

ruveyn wrote:

Eccles_the_Mighty wrote:

But the pythagorians didn't know about \pi, right? They only knew about irrationality of fraction, iirc. Who first discovered that \pi is irracional?

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27 Mar 2014, 11:13 am

ModusPonens wrote:

ruveyn wrote:

Eccles_the_Mighty wrote:

But the pythagorians didn't know about \pi, right? They only knew about irrationality of fraction, iirc. Who first discovered that \pi is irracional?

Eventuall the Pythagoreans discovered that not all numbers (I.E. length ratios and area ratios) were rational.

This of couse was several hundred years before Euclid. Axiomatic geometry got its start with Thales in the sixth century b.c.e.

Euclid published his systemization of Geometry in the 3 rd century b.c.e.

NB: c.e. = common era. b.c.e. = before the common era. Christ is not my savior and lord nor my messaih.

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27 Mar 2014, 11:48 pm

Joe90 wrote:

Bryan Oden?
Thats new to me.

There are two OTHER songs about pi entitled simply "Pi" that I know of.

Kate Bush has a "Pi" song, and so do the music/comedy duo called "Hard'n'phirm". Two completely different songs.

But there isnt really much to understand about Pi. Its just the ratio of the diameter of circle to its circumphrence. If the diameter of the pizza is ten inches then that means that the distance around the edge of the pizza is 31.4 inches. It means that the box it came in has an area of 100 square inches. But the pizza itsself only has an area of 78.5 square inches ( pi times the radius squared= 5x5= 25, 25x 3.14= 78.5 about).

Unless its a square pizza. In which case its area is equal to that of the box it came in.

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28 Mar 2014, 12:55 pm

Sorry, math ret*d here! :lol:

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