### What Is It About π?

March 14 is practically an official π day. Why is that? March is the fourth month of the widely accepted Gregorian calendar and, not incidentally, π ≈ 3.14. There are dissenting voices that claim July 22 as a more appropriate day for the celebration because 22/7 (≈ 3.14286) is a better approximation to the real value of π = 3.14159265358979... which, being irrational and even transcendental, may only be approximated with some degree of precision. It appears like March 14 is taking over. Look at all the attention the day gets:

- Time Magazine
- ThirdAge.com
- CNN
- Boston Globe
- Chicago Tribune
- Wired
- NewScientist
- NPR
- Nature
- PC World
- Smithsonian Magazine
- NCTM Illuminations
- Exploratorium
- CNet
- USA Today
- HuffingtonPost

to name a few. Some outlets also mention that Albert Einstein was born on 14 March 1879.

Over the time I too wrote a few pages featuring π, its properties, appearances, and calculations:

- π is a remarkable number
- The Nature of π and Its Determination
- Calculation of the Digits of π by the Spigot Algorithm of Rabinowitz and Wagon
- Area of a Circle by Rabbi Abraham bar Hiyya Hanasi
- Area of a Circle by Leonardo da Vinci
- Estimating Circumference of a Circle
- Buffon's Noodle Simulation
- The Theorem of Barbier
- Infinite Sums and Products
- Complex number to a complex power may be real

Patrick Vennebush, the author of the hilarious *Math Jokes 4 Mathy Folks*, came up with an amusing math trick and a story:

Write all 26 letters of the alphabet, but start with the letter J:

JKLMNOPQRSTUVWXYZABCDEFGHI

Then, remove all the letters that have vertical symmetry:

JKL N PQRS Z BCDEFG

Now, count the letters that remain in each subset: 3 1 4 1 6.

When I did this trick at a Kâ€‘12 math teachersâ€™ conference recently, I wrote the numbers under each group. But I wasnâ€™t sure that everyone would recognize the digits. So I drew an exaggerated decimal point between the 3 and 1, and I stated, â€œIf you donâ€™t know why this is relevant with Pi Day just around the corner, youâ€™ve really missed the point.â€

is one of the five fundamental constants that appear in the formula e^{iπ}+1=0 that is often judged to be the most beautiful of mathematical identities. Here is another i^{i}=e^{-π/2} of which Augustus De Morgan wrote

Imagine a person with a gift of ridicule. [He might say] First that a negative quantity has no logarithm; secondly that a negative quantity has no square root; thirdly that the first nonexistent is to the second as the circumference of a circle to the diameter.

A History of π by P. Beckmann is one book that should be read by every one curious about the famous and intriguing number π.