Math Constants

Have you ever wondered where the numbers like pi, e, and phi come from? I love the special math constants and I think it's awesome that these numbers, some of which will never repeat and never end, are so useful that we create ways to represent them with the smallest possible round-off error. Pi is my absolute favorite, mostly because of pi day (March 14th) and pi approximation day (July 22nd), but they are all fascinating!
In case you ever want to know any of the four major constants -- pi, e, phi or Euler's constant -- here is a site that lists them all to many more decimals than you could ever need!
PI: Mathworld, one of the sites I recommended earlier, has a site specifically on pi. It goes into a bit of detail about the history of pi, approximations, the more recent culture references to pi and much more. Here is a more detailed history of pi.
e: Although it doesn't have it's own holiday (it's digits just don't work quite as well), e is another very common mathematical constant. e is much easier to approximate and this site not only explains that, but it explains the more recent history and explains how e manifests itself in many situations. Here's Mathworld's take on e, similar in content to the one on pi.
PHI: Phi isn't a number than only the mathematicians of the world can claim. Phi is known as the "golden ratio" and appears in many applications. This site, dedicated solely to phi, has all sorts of information on phi. Look in the math section for how to mathematically derive it, but also check out its history and other applications. Here's Mathworld's take on it.
Euler's Constant: Euler's constant is a much newer constant. It was studied by Leonhard Euler, one of history's most famous mathematicians. Here is a basic overview of the constant, which is represented by gamma, along with how it is derived. Want to know how pi and this constant are different? Read carefully (I'll give you a hint, it starts with an r . . . )! Mathworld is much more detailed about it and it's history.
So what are you waiting for? I hope this gives you a little of my appreciation and amazement toward these cool constants!