- Pi is the number of times the diameter of a circle can be divided into the circumference.
- π = 3.141592653589793238462643 .......
- given by:
- 190 Chinese mathematicians calculated pi to five decimal places.
- 470 Tsu Ch′ung Chi gives the approximation 355/113 to π which is correct to 6 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.