By definition, 
is the ration of the circumference of a circle to its diameter.
is always the same number, no matter which circle you use to
compute it. |
| For the sake of
usefulness people often need to approximate .
For many purposes you can use 3.1459, which is really pretty
good, but if you want a better approximation you can use a
computer to get it. Here's
to many more digits: 3.14159265358979323846. |
The
area of a circle is
|
|
|
| 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. The modern symbol for Pi 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 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
|
