Tuesday, March 14, 2006

Happy Pi Day and Pi Approximation Day

  Pi Day and Pi Approximation Day are two unofficial holidays held in honor of the mathematical constant π (Pi). Pi Day is observed on March 14.

It is sometimes claimed that the Bible states that π=3, based on a passage in 1 Kings 7:23 giving measurements for a round basin as having a 10 cubit diameter and a 30 cubit circumference. Rabbi Nehemiah explained this by the diameter being from outside to outside while the circumference was the inner brim; but it may suffice that the measurements are given in round numbers. Also, the basin may not have been exactly circular.

Pi Approximation Day may be observed on several dates. Pi Day. March 14, written as 3-14 in the United States date format, represents the common three-digit approximation for the number π: 3.14. It is often celebrated at 1:59 p.m. in recognition of the six-digit approximation: 3.14159. Some, using a 24-hour clock, celebrate it at 1:59 a.m. or 3:09 p.m. ( 15:09 ) instead. The "ultimate" pi moment[1] occurred on March 14, 1592 , at 6:53 AM and 58 seconds. When written in American-style date format, this is 3/14/1592 6:53.58, which corresponds to the value of pi to twelve digits: 3.14159265358. However, considering this was well before any kind of standardized world time had been established, and the general public had no concept of π, the occurrence likely went unnoticed[2]. It's the only holiday to honor a number: Pi Day, on 3-14, the beginning digits of the infinite, nonrepeating decimal expansion of pi = 3.1415926... 

                                                    Area of the circle = π × area of the shaded square

The mathematical constant π is a real number which is defined as the ratio of a circle's circumference (Greek περιφέρεια, periphery) to its diameter in Euclidean geometry, and which is in common use in mathematics, physics, and engineering. The name of the Greek letter π is pi (pronounced pie) in English. This spelling can be used in typographical contexts where the Greek letter is not available. π is also known as Archimedes' constant (not to be confused with Archimedes' number) and Ludolph's number.

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