Umm, heh heh, how do you find the circumference of a circle?

[KDOG]

I want to mod my case by cutting a hole in the front panel directly in front of the front fan and then putting some gasket around the cut edge. But I need to find out how long I need to cut the gasket. I suppose there are simpler methods like string, etc... But I want to be exact. And since like most people, I forgot everything I learned in high school I need to know the circumference of say a 4.5" or 5" circle.

 

[Mister T]

2* Pi * Radius

Pi = 3.1452
Radius = diameter divided by 2

 

[KDOG]

HUH? I get 17.2896 inches, that can't be right a 4.5" inch wide circle is not the big around. I must be doing it wrong. Isn't it pie x R squared....let me try that...no thats 23.78 inches.... let me try just pie x R...hmmm 8.64....Maybe its pie x D....14.15....That SOUNDS right. Lets see....

 

[Drekce]

I think that 4.5in measurement is your diameter. you need the radius whichn is half that.

2 * pi * (2.25) = 14.13in

2*pi*r = the area of the circle

pi*r = some lame attempt at geometry

 

[BigJ]

Heh, just to let you know, you weren't performing the right calculations when you were doin 2*pi*radius, The 2*radius part will give you you're diameter, in this case 4.5. So when finding the circumference, you would either do Pi * Diameter or Pi * Radius (Which is Diameter/2) * 2

 

[element]

Jeebus is the skool systam thet bad are is yoo all joking?

first of all Pi is not 3.1452 its 3.14159265 and yes I have that mesmorized and didnt need to look it up. speaking of being mes more eyesed....I look like this right now:

secondly 2pi*r is not the area of a circle, its the circumference. pi*r^2 is the area.

3rd of all:

at people who don't know the difference between diameter and radius.

 

[chickendinner]

<< secondly 2pi*r is not the area of a circle, its the circumference. pi*r^2 is the area. >>



yah thats like 8th grade math

 

[Mday]

the circumference of a circle can be derived using a path integral with the calculus =) then a parametrization, and you get:

integral (from 0 to 2pi) of R d(theta). =)... basically, after the parametrization, an arm of length R which has a pencil at the end, and as you sweep the arm from an angle of 0 radians to an angle of 2pi radians (the entire circle) you get the circumference...

you get 2* pi*R ;-)

the derivation is much more useful, since you can find the length of any arc (of a circle) by just knowing the radius, and the angle it sweeps.

the area can be derived similarly but this time the pencil moves along the arm... (very fast)

 

[notfred]

If you're older than 14 you're a moron.

 

[Derango]

<< If you're older than 14 you're a moron. >>



I can feel the love in the room

 

[Adul]

<< the circumference of a circle can be derived using a path integral with the calculus =) then a parametrization, and you get:

integral (from 0 to 2pi) of R d(theta). =)... basically, after the parametrization, an arm of length R which has a pencil at the end, and as you sweep the arm from an angle of 0 radians to an angle of 2pi radians (the entire circle) you get the circumference...

you get 2* pi*R ;-)

the derivation is much more useful, since you can find the length of any arc (of a circle) by just knowing the radius, and the angle it sweeps.

the area can be derived similarly but this time the pencil moves along the arm... (very fast) >>




mday you dont want to fry this kids poor brain now do you

 

[yakko]

I make my lower minions do the math.

 

[KK]

question for all circle whizzes, the area of a circle is equal to 64*pi*r(squared), what is the radius equal to? I can't seem to come up with an answer for this question. been outta highschool to long.

KK

 

[Rahminator]

C=pi * d

 

[RossGr]

<< irst of all Pi is not 3.1452 its 3.14159265 and yes I have that mesmorized and didnt need to look it up. speaking of being mes more >>



Hummm.... since he is using 2 digits (4.5") as his diameter using more than 3 digits of PI is uselell, for his purposes 3.15 would be good enough. I love people who think that because their calculator spits it out, it means somthing.

 

[Ameesh]

<< Jeebus is the skool systam thet bad are is yoo all joking?

first of all Pi is not 3.1452 its 3.14159265 and yes I have that mesmorized and didnt need to look it up. speaking of being mes more eyesed....I look like this right now:

secondly 2pi*r is not the area of a circle, its the circumference. pi*r^2 is the area.

3rd of all:

at people who don't know the difference between diameter and radius. >>



and worst off all these are the people who are probably complaining about other peoples spelling.


KDOG and Drekce, you should feel really bad

 

[notfred]

<< question for all circle whizzes, the area of a circle is equal to 64*pi*r(squared), what is the radius equal to? I can't seem to come up with an answer for this question. been outta highschool to long.

KK >>



How the hell should we know? You saying something like "the height of a bridge is is 12 times the width of the bridge squared. What's the width of the bridge?"

And the area of a circle is pi*r*r, not 64*p*r*r

if you mean the area of the circle is 64, then the radius is sqrt(64/pi).

 

[Green Man]

I just felt the need to point out that pie are squared...cake are round. Or wait, is it the other way around?

um, carry on.

 

[IJump]

<<

<< question for all circle whizzes, the area of a circle is equal to 64*pi*r(squared), what is the radius equal to? I can't seem to come up with an answer for this question. been outta highschool to long.

KK >>



How the hell should we know? You saying something like "the height of a bridge is is 12 times the width of the bridge squared. What's the width of the bridge?"

And the area of a circle is pi*r*r, not 64*p*r*r

if you mean the area of the circle is 64, then the radius is sqrt(64/pi). >>



The area can not be 64*pi*r^2, it is mathematically impossible. The area is pi*r^2, 64*pi*r^2 would be 64 times the area of that circle.

 

[notfred]

<< The area can not be 64*pi*r^2, it is mathematically impossible. The area is pi*r^2, 64*pi*r^2 would be 64 times the area of that circle. >>



yes, that's why I said "And the area of a circle is pi*r*r, not 64*p*r*r"

 

[element]

<<

<< The area can not be 64*pi*r^2, it is mathematically impossible. The area is pi*r^2, 64*pi*r^2 would be 64 times the area of that circle. >>



yes, that's why I said "And the area of a circle is pi*r*r, not 64*p*r*r" >>



Maybe they mean 64 circles, cause thats the only way it makes sense to me. If it is one circle, then it is 64 times larger than normal, which makes very little sense, it would just have a larger radius.