Math Question

[Tweak]

For those techies out there: What is the mathmatical eqasion (sp?) for finding the exact circumference and middle point of a perfect circle?

I know this sounds like a dumb one, but I can't seem to find anything on it.

 

[mr_bob]

pie(3.14)* r^2(radius) something like that i think that might be for the area

 

[jmarzilli]

circumfrence = Multiply the diameter by pie (about 3.14)

 

[scottm]

circumference is pi x diameter, or 2 x pi x radius. Pi is 3.14159, and radius is 1/2 diameter.

area is pi x radius squared

 

[RatzoRC]

Go around the circle with string, get your lenght right, and put it on a ruler.
Very scientific.

 

[Buggyracer28]

or you can use a compass. Is the circle already made or are you going to make it? To find the center is really simple. All you have to do is find the diameter, divide that by 2 and theres your center of your circle. Easy as that.

so the equation would be D/2=C D=diameter C=center

Circumference is D x pi

 

[Candyman]

OK, I'll assume you have a circle on paper. First, the circumference is as they said. Pi x D.
To find the exact center you'll need a straightedge and a protractor. First, draw a line from one side of the circle to the other. Doesn't matter where it is. Then find the exact center of that line. Draw another line perfectly perpendicular to that line at that center point. That's the diameter of the circle. Then find the exact center point of the second line and that's the center of your circle.

 

[RatzoRC]

Go around the circle with string, get your lenght right, and put it on a ruler.
Very scientific.

I was only kidding.

 

[Candyman]

Kidding, yes. But it would work. Ranks right up there with measuring your rollout when setting the Venom Speed Meter. They have you lay a ruler next to the tire. Push the car so the driveshaft rotates one turn and you just measure how far the car moved. Nothing like good old 18th century techniques.

 

[RatzoRC]

Kidding, yes. But it would work. Ranks right up there with measuring your rollout when setting the Venom Speed Meter. They have you lay a ruler next to the tire. Push the car so the driveshaft rotates one turn and you just measure how far the car moved. Nothing like good old 18th century techniques.

Funny...
That might be why I don't have one.

 

[Plaidfish]

if you already have a circle on paper use a compass to find the center very easily.......make the compass open greater than the cirlcles radius....pick 2 points anywhere on the circumference of the circle and draw 2 arcs that intersect....they should intersect right on the center....I usually draw 3 arcs since your hand may not be super steady on the first 2...if they ALL hit the same point then you know it's right.......thank you for attending drafting 101

 

[.21Rc10GT]

Go around the circle with string, get your lenght right, and put it on a ruler.
Very scientific.

Exactly... I use that all the time... :smoke:

 

[FastEddy]

Cut the circle out and fold it in half, then in half again.
Worked well with my bowling ball.

 

[Candyman]

Cool! So you can fold a bowling ball?
Do you do it with your tongue?

 

[Tweak]

TeeHee. So, if Pi is only approxamite, how definate is the actuall measurment? wow... I think I just mispelled half that post.

 

[Candyman]

It's not that pi is approximate necessarily. It's that it's infinite. For the sake of calculations like this, extending the value of pi that you use to a reasonable amount of decimal places will make the amount of error insignificant. Most of the time, I see it used as 3.14159. But if you have a scientific calculator or use the scientific one on Windows, it has a pi button which takes it out to like a bunch of decimal places.

 

[Tweak]

So it CAN be exaclty accurate, as far as if you could find something that can calculate that far, but the simple calculatio will be so clse it really doesn't matter. sweet.

 

[Lessen]

TeeHee. So, if Pi is only approxamite, how definate is the actuall measurment? wow... I think I just mispelled half that post.

you can probably assume that the end result will be accurate to within one ten thousandth if you use Pi stretched out to hundred thousandths. Of course you could always use 22/7 if you like fractions and are over anal.

So it CAN be exaclty accurate, as far as if you could find something that can calculate that far, but the simple calculatio will be so clse it really doesn't matter. sweet.

exactly.

 

[Plaidfish]

call Tour Andover Controls (TAC) in Carrolton, Tx.......ask for the energy mngmnt dept and ask anyone of them to tell you the exact value of Pi......the guy that runs the dept makes every employee memorize the first 100 numbers of Pi within a year or they get fired.......how'd you like to work for a guy like that??????he knows it to 1000 decimal places......some geeks take that poop too far.......I use a friggin PC if I need calcs that long.....

 

[Lessen]

that's freakin retarded. I hate power hungry people like that.