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Old 2005-10-12, 11:29 AM   #1
sperry
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Default Deede's geometry question
Since she PM'd this to like eleventy billion people it seems, I thought I'd post the solution for everyone.

First, the question:

Quote:
Originally Posted by sti deede
You are super smart, so I'm hopeing you'll be able to help.

I've been hunting for the formula for a the length of a chord online and I can't find it. I need it to finish a site plan I'm working on.

I know the radius of the circle and the length of the arc that I need the chord for.
Now the solution:

Part one is simply the definition for relating arc length, radius, and central angle (in radians).

Part two is how to use that definition with the known radius and arc length to find the chord length.

Just make sure your calculator is in radians mode when using the final equation:

chord length = 2r sin(s/2r)
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Old 2005-10-12, 11:32 AM   #2
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I knew there was a simpler way.....don'tcha love math?
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Old 2005-10-12, 11:38 AM   #3
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Quote:
Originally Posted by ScottyS
I knew there was a simpler way.....don'tcha love math?
Actually, I *hate* math. I had to take 6 quarters of calculus to pass the 3 required classes in college. Math is the single reason I got into computers instead of mechanical/civil engineering or architecture.
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Old 2005-10-12, 11:51 AM   #4
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I can personally vouch for his lack of math skills...
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Old 2005-10-12, 11:58 AM   #5
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Heheh, I guess I should have placed the sarcasm icon in my post......I like math, but I'm scared of it. I took the bare requirements in school, and rarely use it in life.
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Old 2005-10-12, 12:15 PM   #6
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I had to take 7 quarters of those goddamned calculus classes... haven't used it once in the 4+ years I've been out of school now.
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Old 2005-10-12, 12:26 PM   #7
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Quote:
Originally Posted by AtomicLabMonkey
I can personally vouch for his lack of math skills...
So, anyone see a problem w/ the solution? I never trust myself to get stuff like this right.
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Old 2005-10-12, 12:28 PM   #8
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Thanks Scott. I PMed 3 people, not eleventy billion.

Nick's answer appears to the same as yours.
Quote:
Originally Posted by nKoan
I think it is...

x = 2 * radius * sin( arclength / (2*radius) )
Last edited by sti deede; 2005-10-12 at 12:33 PM.
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Old 2005-10-12, 12:34 PM   #9
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Yay for math. I wish I had sweet teachers in school to explain it to me I have a horrible time processing this stuff, but it's so cool.
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Old 2005-10-12, 01:26 PM   #10
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I hate math.

*drills out brain*

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Old 2005-10-12, 08:34 PM   #11
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Math is fun, when it deals with money.
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Old 2005-10-12, 08:59 PM   #12
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Quote:
Originally Posted by dknv
Math is fun, when it deals with money.
I'd like to modify this statement. When it deals with a surplus of money. If there is such a thing.
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Old 2005-10-13, 08:44 AM   #13
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Quote:
Originally Posted by sti deede
I'd like to modify this statement. When it deals with a surplus of money. If there is such a thing.
There seems to be never enough time and never enough money in life. At least if you're not one of the independantly wealthy...
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