Pi

Pi is the number of times the diameter of a circle can be divided into the circumference.

π = 3.141592653589793238462643 .......

given by:

Historical Notes

190 Chinese mathematicians calculated pi to five decimal places.

470 Tsu Ch′ung Chi established pi to 9 decimal places.

1706 William Jones (1675-1749) introduced the symbol "π" in a textbook for the most famous transcendental number, reportedly because it is the first letter of the Greek verb perimetron ("to measure around") from which the word "perimeter" is derived.

1882 Lindemann proved that pi is transcendental.

See also: Circle, Dirac′s Constant, Greek Alphabet, Irrational Number.