I need some mathmatics help! (Wife says that ain't all)

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Ridgerunner
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I need some mathmatics help! (Wife says that ain't all)

Post by Ridgerunner » Thu Jun 26, 2008 9:37 pm

I have Googled and Yahooed my butt off trying to find out how to obtain the length of an arc with a known angle and known radius. I now feel dumber and more confused than when I started!

O.K. here it is: angle = 24degrees; radius is 26. Can anyone give me the formula to find the length of the arc?

I have had enough of reading about radians, subtending angles, moments and etc., all I want is the stupid FORMULA so I can work it out on my own. You guessed it, math was my Achilles heel in high school and what trig I know is self taught as an old fashioned draftsman (pre AutoCAD).

Thanks for any assistance.
Gary

kenh
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Post by kenh » Thu Jun 26, 2008 9:46 pm


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GlennW
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Post by GlennW » Thu Jun 26, 2008 9:49 pm


Ridgerunner
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Post by Ridgerunner » Thu Jun 26, 2008 10:01 pm

Thanks Kenh, that's just what I was looking for. This place is great - ask a question and some kind soul answers in 9 minutes - love it!

Wow Glenn, it doesn't come any easier than that!

Thanks guys,
Gary

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GlennW
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Post by GlennW » Thu Jun 26, 2008 10:24 pm

In simple "machinist's" terms....

Looks like it would be the Sine of 24° X Radius!

Seems simpler than the formulae they show.

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poohbear2767
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Post by poohbear2767 » Fri Jun 27, 2008 12:03 am

Glenn Wegman wrote:In simple "machinist's" terms....

Looks like it would be the Sine of 24° X Radius!

Seems simpler than the formulae they show.
Actually that would equal the CoSine.

You need to convert 24 degrees to Radians then multiply times the Radius.

24 degrees = .41887902 Radians.

.41887902 Radians x 26 inches = 10.89085452 inches

Pooh Bear

Skeeter5000

math formula

Post by Skeeter5000 » Fri Jun 27, 2008 2:16 am

I am not a math wizard, just another way to work this.

radius = 26 makes the dia. 52.

52 x 3.1416 = 163.3632

163.3632 / 360 = 0.4537866

0.4537866 x 24 = 10.890878

Glad you found the answer

toastydeath
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Post by toastydeath » Fri Jun 27, 2008 2:37 am

I had written some stuff proving why radians and also the equations on the websites. Until I accidentally unplugged my computer. Oh well. If anyone's interested, I can do it again.

Long story short, you can't use sine/cosine to do arc length. Also, the equations on the first webpage is correct, and the shortest. If you have a shorter way, it's probably not right.

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GlennW
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Post by GlennW » Fri Jun 27, 2008 5:01 am

Thanks for the correction guys.

I was thinking that my "method" would give you the distance in a straight line rather than an arc, but when I used a conversion calculator to convert one Degree to Radians the answer it gave was 0.01745329 which I thought was also the Sine of 1! Didn't read enough decimal places though! :oops:

Doing other things at the same time and not paying enough attention!

That's where my assumption came from.



Glenn
Last edited by GlennW on Fri Jun 27, 2008 8:30 am, edited 3 times in total.

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hj-meyer
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Post by hj-meyer » Fri Jun 27, 2008 5:33 am

This calculator is also easy to use:

HS-Rechner
http://www.hs-rechner.de/bits_bytes.htm

Image


Hans-Jürgen[/img]

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GearGeek
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Post by GearGeek » Fri Jun 27, 2008 5:58 pm

I like that one! pitty I don't see a mac version :(

I can read german pretty decent but I can't speak much.

Viel Spaß!

~GearGeek

machine48
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Post by machine48 » Fri Jun 27, 2008 8:23 pm

radius x angle x pi/ 180= arc lenght

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