What are all of the mathematical constants that we know of (and what are they used for). By that I mean numbers such as pi, e, y and golden ratio. And could somebody please tell me how to create mathematical symbols and formulas on this site? I know it's possible, I've seen people do it on this site before.

I think there are too many to list here, or anywhere really. Some of the more important ones:

 

h, or h-bar used in quantum mechanics, alpha the fine structure constant, ditto,

e for differential equations amongst many things, avagadro's constant, phi whihc approximately occurs in nature, for a good explanation about it and its implications as to why it occurs in nature see http://www.maa.org and look up some of devlin's old articles.

 

the maths symbols are mark up thingummies enclosed between some tags. Next time you see one you want to look at click on in and you ought to get the code for it.

thanks, but what do each of them equal (ex. π≈3.141592654), and how exactly are they used (πr²=a)?

You can't say what they are all equal to exactly in decimal expansions. Anyway, I think you should pick the ones you care about and google for them.

Well, I'm more interested in π, e, y, and Ф, and one's like those, but I'll try a search.

I didn't try google, because they always give me too many things, I need my seaches a little narrower, so I chose MSN, and didn't find anything good. But maybee I need to look through all of the results.