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General Forums => The O' Club => Topic started by: lasersailor184 on August 05, 2008, 09:57:53 AM

Title: Geometry help, Arc lengths and chords
Post by: lasersailor184 on August 05, 2008, 09:57:53 AM

Hi O'Clubbers!


I'm trying to figure out the area of an arc with known length, and a chord which touches the ends of the arc.


The chord length is 156', and the arc length is 187'.  I USED to be able to figure this out in Autocad, however everytime I go back they change it on me.  I am unable to find the function to do this anymore.


So what's the equation / program to figure this out?

Title: Re: Geometry help, Arc lengths and chords
Post by: VonMessa on August 05, 2008, 10:21:07 AM

Find the total sector area (of the circle your arc would make)  ----------    Length of arc  =   q   
                                                                                                                2pr              360
 
your chord will give you a triangle within the sector

Figure out the triangle area and subtract it from the total sector area.    :aok

Sorry about the crappy equation representation

Title: Re: Geometry help, Arc lengths and chords
Post by: lasersailor184 on August 05, 2008, 10:35:50 AM

Well, I sort of winged it.  The big problem was that I didn't know theta, nor the radius.  However, I got an area of about 4,700 ftsquared approx, due to the fact that It was chain link fence (not an actual circle). 

I knew how to find Chord/ArcLength.  But I had to fudge the Theta til I found out what it was. 

Title: Re: Geometry help, Arc lengths and chords
Post by: VonMessa on August 05, 2008, 10:41:11 AM

A-ha.

Edit:

I actually had to think about it, also   :lol

I, also have gotten pretty mush-headed from using auto-cad.  It's much easier to pull dims from the cad program.    :aok

Title: Re: Geometry help, Arc lengths and chords
Post by: Chalenge on August 05, 2008, 11:47:29 AM

Im pretty sure (without opening ACAD) that you can use the arc command to construct your arc with the known chord and then the area is pretty easy to calc (or just hatch it and get the area of the hatch). There has to be at least one-hundred ways to do this.

Title: Re: Geometry help, Arc lengths and chords
Post by: lasersailor184 on August 05, 2008, 12:56:52 PM

Quote from: Chalenge on August 05, 2008, 11:47:29 AM

Im pretty sure (without opening ACAD) that you can use the arc command to construct your arc with the known chord and then the area is pretty easy to calc (or just hatch it and get the area of the hatch). There has to be at least one-hundred ways to do this.

I know there were.  But I don't have access to Autocad.

Title: Re: Geometry help, Arc lengths and chords
Post by: acfireguy26 on August 05, 2008, 01:03:45 PM

 :huh

Title: Re: Geometry help, Arc lengths and chords
Post by: Chalenge on August 05, 2008, 10:59:05 PM

Quote from: lasersailor184 on August 05, 2008, 09:57:53 AM

I USED to be able to figure this out in Autocad, however everytime I go back they change it on me.  I am unable to find the function to do this anymore.

Sorry these two sentences led me to believe you were trying to do this in AutoCAD.