# 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 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.*

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

**Subjects: ** Mathematics