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Pi
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last edited
by PBworks 16 years, 4 months ago
What Is Pi???
What is pi ()? Who first used pi? How do you find its value? What is it for? How many digits is it?
By definition, pi is the ratio of the circumference of a circle to its diameter. Pi is always the same number, no matter which circle you use to compute it.
For the sake of usefulness people often need to approximate pi. For many purposes you can use 3.14159, which is really pretty good, but if you want a better ;
approximation you can use a computer to get it. Here's pi to many more digits: 3.14159265358979323846.
The area of a circle is pi times the square of the length of the radius, or "pi r squared":
A = pi*r^2
A very brief history of pi.
Pi is a very old number. We know that the Egyptians and the Babylonians knew about the existence of the constant ratio pi, although they
didn't know its value nearly as
well as we do today. They had figured out that it was a little bigger than 3; the Babylonians had an approximation of 3 1/8 (3.125), and the
Egyptians had a somewhat
worse approximation of 4*(8/9)^2 (about 3.160484), which is slightly less accurate and much harder to work with. For more, see A History of Pi by Petr Beckman (Dorset Press).
The modern symbol for pi [] was first used in our modern sense in 1706 by William Jones, who wrote: There are various other ways of finding the Lengths or Areas of particular Curve Lines, or Planes, which may very much facilitate the Practice; as for instance, in the Circle, the Diameter is to the Circumference as 1 to (16/5 - 4/239) - 1/3(16/5^3 - 4/239^3) + ... = 3.14159... = (see A Historyof Mathematical Notation by
Florian Cajori).
Pi (rather than some other Greek letter like Alpha or Omega) was chosen as the letter to represent the number 3.141592... because the letter [ ] in Greek, pronounced
like our letter 'p', stands for 'perimeter'.
About Pi.
Pi is an infinite decimal. Unlike numbers such as 3, 9.876, and 4.5, which have finitely many nonzero numbers to the right of the decimal place, pi has infinitely many
numbers to the right of the decimal point.
If you write pi down in decimal form, the numbers to the right of the 0 never repeat in a pattern. Some infinite decimals do have patterns - for instance, the infinite
decimal .3333333... has all 3's to the right of the decimal point, and in the number .123456789123456789123456789... the sequence 123456789 is repeated. However,
although many mathematicians have tried to find it, no repeating pattern for pi has been discovered - in fact, in 1768 Johann Lambert proved that there cannot be any
such repeating pattern.
As a number that cannot be written as a repeating decimal or a finite decimal (you can never get to the end of it) pi is irrational: it cannot be written as a fraction (the
ratio of two integers).
Pi shows up in some unexpected places like Probablityand the 'famous five' equation connecting the five most important numbers in mathematics, 0, 1, e, pi, and i: e^
(i*pi) + 1 =0.
The name of the greek letter is pi, and this spelling is used in tyrographical contexts where the Greek letter is not available or where its usage could be problematic. When referring to this constant, the symbol π is always pronounced like "pie" in english , the conventional English pronunciation of the letter. In Greek, the name of this letter is pronounced slightly differently.
The constant is named "π" because it is the first letter of the greek words περιφέρεια 'periphery'[1] and περίμετρος 'perimeter', i.e. 'circumference'. π is unicode character U+03C0 ("greek small letter pie").[2]
Computers have calculated pi to many decimal places. here are 50,000 of them and you can find many more from Roy Williams' Pi page.
Pi
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Comments (23)
Anonymous said
at 8:53 am on Oct 29, 2007
wow lots of unuseful words your wiki is good but why do we need to about ejuptions and the bablionian people other than that your wiki is good and reallly long
Anonymous said
at 1:59 pm on Oct 29, 2007
i like the picture of the pie sign its ballin
Alex L. said
at 7:27 pm on Oct 30, 2007
Good job, you have a nice long explantion
Anonymous said
at 5:23 pm on Oct 31, 2007
cool pi sign. Whos alex? He has a weird face next to his name.
Anonymous said
at 5:41 pm on Oct 31, 2007
pretty pi pic
Anonymous said
at 9:57 am on Nov 5, 2007
i like the pie pic. it cool
Anonymous said
at 10:04 am on Nov 5, 2007
You have a lot on the history of Pi and it kind of takes over the page
Anonymous said
at 10:12 am on Nov 5, 2007
I like ur page cuz it has lotz of info but i think yu should use different colors and be creative bout it...
but i love the picture at the bottom...
Anonymous said
at 1:06 pm on Nov 5, 2007
there are too many words, try organizing it diffrently. but its still good. :)
Anonymous said
at 1:08 pm on Nov 5, 2007
Very nice info and I like the big picture on the bottom, but I think you should make it more eye-catching with more colors and some more about the equation. Some more pictures would be nice too ^^
Anonymous said
at 1:32 pm on Nov 5, 2007
looks great you covered all the information clerly and thoroughly.
Anonymous said
at 2:25 pm on Nov 5, 2007
nice pi symbol, but you can do better than regular black words
Anonymous said
at 2:26 pm on Nov 5, 2007
it's very nice, but you need a heading, so that the teacher will like it more.
Anonymous said
at 2:35 pm on Nov 5, 2007
pleese chand the color...
its gonna give some one a seizure...lol
it looks really goo though...
Anonymous said
at 2:36 pm on Nov 5, 2007
Change the light blue, it can't read it.
Anonymous said
at 2:38 pm on Nov 5, 2007
hey matt i think you should change the part where it says 'history of pi' because it's hard to read. also the pard after that with the light green. it's pretty good tho.
Anonymous said
at 2:38 pm on Nov 5, 2007
check spelling + capitals
Anonymous said
at 2:38 pm on Nov 5, 2007
OH! and a question mark after 'WHAT IS PI' as your title.
Anonymous said
at 2:45 pm on Nov 5, 2007
things are a bit too large for my computer screen, nice info though
Anonymous said
at 2:56 pm on Nov 5, 2007
Try not to copy what you find online completly. try paraphrazing
Anonymous said
at 4:50 pm on Nov 5, 2007
It looks pretty good, but you might want to make the first picture of pi a little smaller, it takes up pretty much of the screen when you're scrolling down. You can also make your subheadings, such as "What is Pi", bigger and bolder.
Anonymous said
at 5:05 pm on Nov 5, 2007
nice. but the colors are kind of odd. first you have red then you have that bluish greenish color. and the picture of pi is WAAAYY to big. so yeah. anyways. it's good.
Anonymous said
at 10:26 pm on Nov 14, 2007
Matt, too much of the content of your page is not in your own words. You need to paraphrase as Nello said. You would have given us a more clear understanding of pi than these people who wrote your page have.
I like the way you started your page with the questions about pi. You should organize your page with the answers to those questions and formating that shows which question you are answering.
1 of 4 points.
9 of 12 total project points.
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