NCAAF  > General NCAAF  > Math help ?
November 19, 2010, 05:54 PM
Sorry about making this nonsports thread here, but you guys seem the smartest bunch on FN, and might be able to help me.

Does anyone know the formula for finding the radius of an arc ?

I had it wrote down in a couple of notebooks, one was in the shop that a tornado hit, and the rain washed all the ink off, dammit ! And the other one I can`t find, dammit there too !

It was something like; width x 2 divide by hieght + half of hieght, blah blah blah.

I didn`t use it a lot, but when I needed it like today, and couldn`t find it, I see how handy it was, thanks if you can help.
November 19, 2010  06:10 PM ET

Thanks for a simple question. Found this on the internet
radius

Rise2 + (Span/2)2
_________________
2 x Rise

For instance, let??s assume that an arched opening leading from a dining room to the great room has 84-inch tall sides, the span is 96 inches and the center of the arch is to be 96 inches above the floor.

The rise is then 12 inches, as shown in the drawing.

When you substitute the numbers and calculate the formula you get:

Rise2 + (Span/2)2
_________________
2 x Rise



122 + (96/2)2
________________
2 x 12



144 + 482
_______________
24



144 + 2304
______________
24



2448
___________
24



102



The radius is 102 inches - with no errors resulting from inadvertent stretching of chalklines or other mechanical limitations, such as trying to lay out a curve with a 102-inch radius on a piece of plywood that??s only 96 inches long.

- Charles W. Davis, Watsonville, Calif.

November 19, 2010  06:15 PM ET
QUOTE(#2):

Thanks for a simple question. Found this on the internetradiusRise2 + (Span/2)2_________________2 x RiseFor instance, let??s assume that an arched opening leading from a dining room to the great room has 84-inch tall sides, the span is 96 inches and the center of the arch is to be 96 inches above the floor.The rise is then 12 inches, as shown in the drawing.When you substitute the numbers and calculate the formula you get:Rise2 + (Span/2)2_________________ 2 x Rise122 + (96/2)2________________ 2 x 12144 + 482_______________24144 + 2304______________242448___________24102The radius is 102 inches - with no errors resulting from inadvertent stretching of chalklines or other mechanical limitations, such as trying to lay out a curve with a 102-inch radius on a piece of plywood that??s only 96 inches long.- Charles W. Davis, Watsonville, Calif.

Confusing...that is rise squared....so the rise is 12 and squared, of course, is 144...
but you were close. Determine the length of the opening....half that and measure the rise from that point. Then the rise squared plus the length halved and the squared...this is then dived by the length doubled.

November 19, 2010  06:15 PM ET

Oh...and go Sooners and State....

November 19, 2010  06:34 PM ET

looks like this has the info you need, Jim

radius of an arc
http://www.mathopenref.com/arcradius.html

arc length (distance along the curved part of the arc)
http://www.mathopenref.com/arclength.html

November 20, 2010  01:56 AM ET

Just out of curiosity,
Why are you trying to find the radius of an arc?

November 20, 2010  02:49 AM ET

Ah.
You must have 1 hell of a job.

November 20, 2010  11:14 AM ET
QUOTE:

thats the craziest formula yet !!!!! There is now way I can understand that !!!!!C`mon man, simplify that crap !

LOL! Just made my day, CussWord

November 22, 2010  11:55 AM ET

The things you learn on FanNation...

:)

November 22, 2010  09:17 PM ET
QUOTE:

whoo-hoo ! I found it, this is it in case anybody was curious;Width x itself, divide by 8, divide by height, plus half of height.

That's what I said....wasn't it? Or was it?

Go somebody....now I'm confused.

November 22, 2010  09:35 PM ET

Oh man. That is a whole lesson in of itself. And I can't do mathematical explanations without my chalk and board.

November 22, 2010  09:40 PM ET
QUOTE(#17):

The things you learn on FanNation...:)

We make Wikipedia look like a class act ...

November 23, 2010  10:11 AM ET

Yeah, but we have MUCH more personality...

November 29, 2010  04:28 PM ET
QUOTE:

D2, I have no idea if that is what you said, I asked for a simple way to figure that, cause I`m not smart enough to understand the stuff you put up, sorry, and if you`re just trying rip on me being dumb, well, I`m to dumb to get that also.

Simple one here:

http://mathcentral.uregina.ca/QQ/database/QQ.09.98/riddleberger1.html


radius = (4 x height^2 + Length^2) / (8 x height)

November 29, 2010  04:34 PM ET

I need help with this math problem. Team A is favored in two polls by one spot. Team B is favored in 6 polls by one spot. The two polls for Team A are each weighted 6 time each of the polls for team B. The 6 polls for Team B are equivalent to 1/2 the combined polls for Team A. Taking an average of all of the polls,

Team A with the higher rank in the majority-weighting of polls < team B with the higher rank in the minority-weighting of polls.

November 29, 2010  04:40 PM ET
QUOTE:

hey Grue, what does the ^ mean ? I found my formula that is spelled out for me, but another formula would be great to also.I had basic math my senior year, my boys had that class in 7th grade, so my knowledge is not much, and then I have damaged it with booze.

^2 is the keyboard equivalent of Squared.

radius = [(4 x height x height) + (Length x Length)]
..............__________________________________
.................................(8 x height)


Better?

November 29, 2010  04:40 PM ET
QUOTE:

hey Grue, what does the ^ mean ?

"Raised to the power of"

so height^2 is height squared.

November 29, 2010  04:42 PM ET
QUOTE:

lol........ok, never mind, your mocking me so it is all dumb, I`ll go now, ha !

No, I'm mocking the BCS. I honestly cannot figure out how Auburn jumped Oregon when Oregon is higher ranked in the majority of the weighting.

November 29, 2010  06:08 PM ET
QUOTE:

D2, I have no idea if that is what you said, I asked for a simple way to figure that, cause I`m not smart enough to understand the stuff you put up, sorry, and if you`re just trying rip on me being dumb, well, I`m to dumb to get that also.

It was a joke man...not ripping on you at all. Wish I could make cabinets...or anything with wood. Envy you guys who can and make it look easy....

November 29, 2010  06:11 PM ET
QUOTE:

better, but still confusing, maybe once I sober up I can understand better.........but I told my teacher at school the same thing !

Tell GR what it is you're drinking so he can have it at the Ice Haus.....sounds serious.

 
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