p is the symbol used for this special number Pi is its name
(pronounced `pie')
p comes from working with circles.
p is the ratio of the circumference of a circle to its
diameter.
This means that you can work out p by dividing distance around
a circle by the length of its diameter. The strange thing is that
the answer you get can only ever be approximate - that is, you can
never have an exact value for pi. This has fascinated
mathematicians for a very long time and they have kept trying to
find ways to calculate values for pi that are more accurate.
p is needed to find the area of a circle using the
formula pr2
To work out the area of a circle you need to use an approximate
value for pi (like 3.14) then multiply that by the radius of the
circle squared. For example; if the radius was 5 cm, the area
would be 3.14 × 5 × 5 ×78.5 square centimetres.
What is the value of Pi?
In the Old Testament of the Bible (I Kings 7:23) it is suggested
that p is equal to 3. The Babylonians, in about 2000 BC, use 3
or 3 1/8.In the ancient Rhind papyrus, the Egyptian scribe Ahmes
said that p was equal to 16/9 squared. This calculates to
3.16049....
Archimedes worked on the problem of finding p by calculating
the area of regular polygons, with up to 96 sides. He decided that
p was somewhere between 310/71 and 310/70. In decimals this
would be 3.14085... and 3.142857... (remember the decimal places
keep going on and on).
Over the centuries, many mathematicians, such as Ptolemy (the
ancient Greek astronomer), Tsu Ch`ung-Chi (of China) and Ludolph
van Ceulen (of Germany) kept trying to find more accurate values
for pi using a variety of different methods. During the last few
centuries people have been trying to find as many decimal places
as possible so they can look for patterns in the long string of
digits. In 1949 a computer was used to calculate pi to 2,037
places. In 1967 in France 500,000 digits were found. In 1983 a
Japanese team found 16, 777, 216 decimal places for pi. The current record is
about 51 billion
decimal places.
Here are some of the decimal places that have been found:
To help remember these digits, people like to make up sentences or
rhymes, called mnemonics.
For example, ``May I have a large container of coffee?'' is quite
a famous one for the first eight digits. You work out the numbers
by counting the letters in each word.
Here`s one for the first 31 digits:
``Now I will a rhyme construct,
By chosen words the young instruct.
Cunningly devised endeavour,
Con it and remember ever.
Widths in circle here you see,
Sketched out in strange obscurity.'' Try making up your own mnemonic for the digits of pi.
To find out more about pi, have a look at Eric's Encyclopedia of
Mathematics- click on P, then find pi in the list and click.
http://www.treasure-troves.com/math/math.html
