I need some mathmatics help! (Wife says that ain't all)
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 Joined: Thu Mar 16, 2006 11:11 pm
 Location: Near Atlanta, yet far enough away!
I need some mathmatics help! (Wife says that ain't all)
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
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

 Posts: 120
 Joined: Thu Mar 16, 2006 11:11 pm
 Location: Near Atlanta, yet far enough away!
 poohbear2767
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 Location: Dunlap TN (Chattanooga area)
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Actually that would equal the CoSine.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.
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
math formula
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
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

 Posts: 176
 Joined: Fri Aug 10, 2007 8:00 pm
 Location: Newark, DE
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.
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.
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!
Doing other things at the same time and not paying enough attention!
That's where my assumption came from.
Glenn
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!
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.
This calculator is also easy to use:
HSRechner
http://www.hsrechner.de/bits_bytes.htm
HansJürgen[/img]
HSRechner
http://www.hsrechner.de/bits_bytes.htm
HansJürgen[/img]