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Where does pi come from?


Date: 13 Jan 1995 13:17:34 -0500
From: Kavita George
Subject: (none)

        I was wondering how exactly the math notation pi was 
derived and whoever derived it, why did he make up that symbol for pi?
Please answer this small question of mine by Jan 17. and mail it to 
kgeorge@walrus.mvhs.edu

                                      Sincerely
                                                  Ms. Kavita George

Monta Vista High School - kgeorge@walrus.mvhs.edu


Date: 14 Jan 1995 00:37:37 -0500
From: Dr. Ken
Subject: Re: your mail

Hello there!

The the Greek letter {Pi} (when I write that, I mean the symbol that you're
used to seeing for Pi) was first used by a man named William Jones in 1706.
He lived in England at the same time as Isaac Newton (who also lived in
England), and he used the symbol {Pi} in a book called "A New Introduction
to the Mathematics."  He said that the work was intended "for the Use of some
Friends who have neither Leisure, Convenience, nor, perhaps, Patience, to
search into so many different Authors, and turn over so many tedious
Volumes, as is unavoidably required to make but tolerable progress in the
Mathematics."

The Greek letter {Pi} is pronounced like a p in English.  So it is widely
believed, both in light of that fact, and in the way that Jones used it in
his work, that {Pi} was used as an abbreviation for the English word
"periphery."  He used the word periphery the same way we now use
circumference and perimeter for the distance around a circle and a polygon.

However, Williams Jones was no heavyweight in the math world, and nobody
really paid much attention to his use of the letter {Pi}.  It wasn't until
1737 that Leonhard Euler (a big math heavyweight - one of the most
revolutionary mathematicians who ever lived) used it, and then it gained
pretty wide acceptance.

I got most of my information from the book "A History of Pi" by Petr
Beckmann, and if you're interested in learning more about Pi, I recommend
you check it out.  Thanks for asking!

-Ken "Dr." Math
__________

Date: 14 Jan 1995 00:42:05 -0500
From: Dr. Ken
Subject: Re: where did Pi come from?

Hello there!

Here's some more information on Pi that we (actually, that Ausgezeichnet
math doctor Sydney wrote it by herself) gave as an answer to a previous
question.  Enjoy!
__________

Date: Mon, 5 Dec 1994 15:09:11 -0500 (EST)
From: Dr. Sydney
Subject: Re: question

     Pi is defined to be the ratio of the circumference of a circle to the
diameter of a circle.  Say you have a circle of radius 1.  Then the
circumference of the circle is 2Pi(1) and the diameter is 2(1), so the
ratio of the circumference to the diameter is Pi.  Anyway, Pi is an
infinite decimal that is approximately equal to 3.14.

     People have worked on approximating Pi for thousands of years.
For instance, Archimedes approximated Pi by inscribing polygons in
the circle and taking the ratio of the circumference of the polygon to the
radius of the circle (which is also the "radius" of the polygon).  The more
sides on the polygon, the more accurate the approximation.  So, if you
inscribe a dodecagon (12-sided polygon) and compute the ratio of the
circumference to the radius, you will get a better approximation than if
you do the same for a hexagon (6 sides).

     This makes sense if you draw it out.  The polygons with the greater
number of sides more closely resemble circles.  It is important to
remember Pi does not equal 3.14; instead, 3.14 is an approximation for Pi.
Really Pi = 3.141592653... (it is an infinite decimal).

Mathematicians began notating this ratio with the Greek letter Pi around
1706.  Perhaps the letter Pi was chosen to represent "periphery" (Pi is the
ratio of the circumference (periphery) to the diameter).

     I hope this helps.  If not or if you have any other questions, please feel
free to write back.  Thanks!

--Sydney, Dr. "Math Rocks"

-Ken "Dr." Math
    
Associated Topics:
High School History/Biography

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