Associated Topics || Dr. Math Home || Search Dr. Math

### Where did Pi come from?

```
Date: Fri, 2 Dec 1994 10:20:16 EST
From: 904
Subject: question

Good day, Dr. Math:

We are an adult high school and we were wondering if you could answer
our question.  Where did the word pi come from, and how did someone
determine it was equal to 3.14?

Thank you,
Margie at TCLFLA5.
```

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

Dear Margie:

Thanks for writing Dr. Math!  We are more than happy to answer

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"
```
Associated Topics:
High School History/Biography

Search the Dr. Math Library:

 Find items containing (put spaces between keywords):   Click only once for faster results: [ Choose "whole words" when searching for a word like age.] all keywords, in any order at least one, that exact phrase parts of words whole words

Submit your own question to Dr. Math
Math Forum Home || Math Library || Quick Reference || Math Forum Search