# Pi Day

## Pi and its symbol

The symbol used by mathematicians to represent the ratio of a circle's circumference to its diameter is the Greek letter π, sometimes spelled out as pi, particularly when foreign fonts are not available.

## Pi's Value Ratio

Succinctly, pi--which is written as the Greek letter for p, or --is the ratio of the circumference of any circle to the diameter of that circle. Regardless of the circle's size, this ratio will always equal pi. In decimal form, the value of pi is approximately 3.14

## Pi (Continue Infinitely)

That pi is an irrational number does mean it will continue infinitely without repeating. For all rational numbers, and only rational numbers, the decimal representation of the number will at some point start repeating and keep repeating, e.g., 3.1415926926926926926

## Pi (Irrational Number)

Rational numbers can be expressed as a fraction with an integer in both the top and the bottom. Just expressing it as a fraction is not adequate. For example: pi/2 is a fraction but it is irrational.

## Pi's Digits

Because Pi is known to be an irrational number it means that the digits never end or repeat in any known way. But calculating the digits of Pi has proven to be an fascination for mathematicians throughout history. Some spent their lives calculating the digits of Pi, but until computers, less than 1,000 digits had been calculated. In 1949, a computer calculated 2,000 digits and the race was on. Millions of digits have been calculated, with the record held (as of September 1999) by a supercomputer at the University of Tokyo that calculated 206,158,430,000 digits. (first 1,000 digits)

## Mathematicians and Pi and Why

David Gregory (1697) used π/r for the ratio of the circumference of a circle to its radius. The first to use π with its present meaning was an Welsh mathematician in 1706 when he states William Jones "3.14159 andc. = π". Euler adopted the symbol in 1737 and it quickly became a standard notation.

## Record of Pi's Digits

"What I am aiming at is not just memorizing figures, I am thrilled by seeking a story in pi," Haraguchi said. The Guinness Book of Records currently lists Hiroyuki Goto , also from Japan, as the official record holder for reciting pi from memory. He recited the ratio out to 42,195 decimal places in 1995.

## Pi's Celebration

Pi Day is celebrated every year on March 14 because the first three digits of pi are three, one and four, much as the date is represented numerically as 3/14. The constant is also represented by the Greek letter π.