Pi- the greek letter

[Shrykull]

I was wondering exactly who invented pi (was it Euclid, because they call it Euclidian Geometry) and how did he know that it times the radius of a circle squared would give you the area of a circle? I'm guess it really doesn't give the exact area, that pi is just an approximation of whatever it's supposed to stand for.

[Wicked Pilot]

I was wondering exactly who invented pi (was it Euclid, because they call it Euclidian Geometry) and how did he know that it times the radius of a circle squared would give you the area of a circle? I'm guess it really doesn't give the exact area, that pi is just an approximation of whatever it's supposed to stand for.

Look it up.

[Colonel Olrik]

I was wondering exactly who invented pi (was it Euclid, because they call it Euclidian Geometry) and how did he know that it times the radius of a circle squared would give you the area of a circle? I'm guess it really doesn't give the exact area, that pi is just an approximation of whatever it's supposed to stand for.

Pi has been known since long before the greeks. The degree of exactitude varied, from 3 to 3.2 several were the considered values.

Euclides had nothing to do with it. Eunclidian geometry has nothing to do with it.

pi gives the exact data. But, being an irrational number, an aproximation must always be used. The error can be made as low as it is wished.

[Sonnenburg]

http://www.straightdope.com/mailbag/mpiorigin.html

[Slartibartfast]

I was wondering exactly who invented pi (was it Euclid, because they call it Euclidian Geometry) and how did he know that it times the radius of a circle squared would give you the area of a circle? I'm guess it really doesn't give the exact area, that pi is just an approximation of whatever it's supposed to stand for.

Actually it's the other way around: they knew the cicumference of a circle, and knew its area, and figured out a constant that in every case will give you either. Not sure how a computer figures it out, I think it's a special formula.

But IIRC, the Greek didn't use decimals, they figured it was something like 10/3 (ten thirds).

EDIT: I just remembered, it wasn't 10/3, somebody figured out that "Pi" (IF it was even called that) was 25/8.

[Malecoda]

What do you mean "how a computer figures it out. It must be a special formula"? If you know the circumference and the area, you can figure it out. The computer can't figure anything out, you have to tell it the formula beforehand. So there's some number, let's call it pi, that we don't know. But obviously, the diameter of a circle has a ratio to the circumference, so d = pi*C, with pi to solve for. So pi = d/C, or 2r/C. Is the question more complicated than I am seeing?

Say you know the area and the radius, but you don't know pi. It may have been some leap of insight for someone to say "maybe you should square the radius, since that's the same approach to the area of a square." You can see that I don't know for sure, but this is how to figure it out and I'm running with it. So A = pi*r^2, for some unknown pi. Solve. Are the "pi as a function of C" and "pi as a function of A" expressions equivalent? Substitute pi*r^2 for A and 2pi*r for C and you get this big uh, circle that gives you a trivial response of pi.

Could be wrong. Could be circular. For the true story, instead of figuring it out (last time I showed some people in here how to figure stuff out ON THEIR VERY OWN, they cried like bitches), I say look it up. Oh look, it's been said. Look it up.