2. What is Pi?
• Pi is defined as the ratio
of the circumference to
the diameter of a circle
• Pi is usually denoted
with this greek symbol:
π
π =
circumference
diameter
4. History of Pi
• The hunt for pi began in Egypt and in Babylon
about two thousand years before Christ. The
Egyptians obtained the value (4/3)4 and the
Babylonians the value 3 1/8 for pi. About the
same time, the Indians used the square root of
10 for pi. These approximations to pi had an
error only as from the second decimal place.
5. Who Discovered Pi?
• Archimedes was the first to
theoretically approximate pi
• He calculated that pi was
“trapped” between 223/71 and
22/7, or roughly 3.1428
• Today we use better
approximations, most of
which are derived by
computers
Hi, I’m
Archimedes…
Pi = Between
223/71 and 22/7
6. The Death of Archimedes
Archimedes was born in 287 BC in a Greek
state called Syracuse, Sicily.
The city of Syracuse was taken over by the
Romans and Archimedes was killed.
It is said that he was busy drawing circles in
the dust and writing mathematical equations
at the time of his death
THAT’S HOW IMPORTANT PI
WAS TO ARCHIMEDES!!!!!
7. THE DISCOVERY OF PI
Who? When? Discovery Equivalence
Egyptians 2000 BC (4/3)4
3.160493827...
Babylonians 2000 BC 3 1/8 3.125
Indians 2000 BC
square
root of 10 3.16227766...
Archimedes 250 BC 22/7 3.14128…
Computers Today Pi 3.1415926535…
Currently the value of pi is known to 6.4 billion places!
8. The Usefulness of Pi
• Pi is extremely useful in calculating the area
and circumference of a sphere: A = πr2 and
C = 2πr.
• Many disciplines of science use π in their
equations to describe the world
• In fact DNA, rainbows, the human
eye, music, color, and ripples
all have some natural roots in pi.
9.
10. Diameter and Radius
• The distance across a circle
through its center is called its
diameter, D.
• The radius, R of a circle is the
distance from the center of a
circle to a point on the edge of
the circle.
• So a circle's diameter is twice
as long as its radius: D = 2 × R.
diameter, D
radius, R