### 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 K‑12 math teachers’ conference recently, I wrote the numbers under each group. But I wasn’t sure that everyone would recognize the digits. So I drew an exaggerated decimal point between the 3 and 1, and I stated, “If you don’t know why this is relevant with Pi Day just around the corner, you’ve really missed the point.”

\pi 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.