    # 3.14159265358979323846264338327950288419

## A Cultural Phenomenon

π is a matter of national obsession, inspiring books, movies, memorization contests, and quests to find more digits in quicker and better ways. π has even made its appearance on The Simpsons!

In one episode, "Kwik-E-Mart proprietor Apu brags that he can recite pi to 40,000 decimal places. 'The last digit is 1,' he announces. To get that detail right, the Simpsons writing team faxed a query to NASA, where mathematician David Bailey obliged with the digit in question". Read more about math found in The Simpsons within the Science News Online article "Springfield Theory".

## Running Circles 'Round the Competition

π has everything to do with a perfect circle. It is the ratio of the circumference of the circle to its diameter, and it is needed for practically every calculation involving circles. It is an integral part of trigonometry, and it is exactly half the time it takes for the sin(x) and cos(x) wave functions to repeat themselves. We now know pi to over a trillion decimal places, and are continuously developing new algorithms to make the calculations quicker and more elegant.

## Shape Formulae Involving π:

circle:

• Circumference= 2π r
• Area= π r2
• sphere:

• Volume= 4/3 π r3
• Surface Area=4π r2
• cone:

• Volume= 1/3 π r2 h
• Surface Area= π r (r + √(r2 + h2))

## Other Formulae

• cos(π)=-1
• sin(π)=0
• integral(-1 to 1) dx/√(1-x2) = π
• integral(-inf to inf) e-x2dx=√π
• The formula for the normal statistical bell curve involves π.