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June 28th, 2013, 03:25 AM   #1
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Circle segment area

Hi there
Problem:
Of a circle segment is known: Area and radius.
Wanted:
Height from the circle circumphere ot the chord.

I know the formula for the circle segment it is to found everywhere.

But how do I resolve it to return the height ?

NOTE: the angle is NOT known.
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June 28th, 2013, 04:08 AM   #2
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Re: Circle segment area

You can find the angle in radians using



Then use that angle to find the height of the isosceles triangle

Then subtract that from the radius.

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June 30th, 2013, 12:03 AM   #3
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Re: Circle segment area

It is a circle segment not sector.

If I: A/0.5*r^2= (radians-Sin(radians)

How do I get the radians out ?
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June 30th, 2013, 03:00 AM   #4
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Re: Circle segment area

Quote:
Originally Posted by Pivskid
It is a circle segment not sector.

If I: A/0.5*r^2= (radians-Sin(radians)

How do I get the radians out ?
If you know A and you know r then is in radians automatically.

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June 30th, 2013, 11:35 PM   #5
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Re: Circle segment area

Yes, it is radians.

But radians from a area of a circle sector not a segment.

The result is that I get a redicously narrow angle.
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July 1st, 2013, 11:20 AM   #6
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Re: Circle segment area

Post your calculations please so that we can check them.

If i now understand you correctly ,



You have A , you have r so now you want to solve for in radians.

Is that right?

If that's right , you can only get an approximation , there is no way i know of to get an exact solution.

There may be a different approach to get the height that i don't know about , you don't have the length of the chord , do you?

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July 1st, 2013, 10:31 PM   #7
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Re: Circle segment area

It is a "real life" scenario where a horizontal positioned vibrating tube is filled with a product, could be flour, or sugar.
The tube transports the product, such as conveyour belt.

I'm the programmer of the controling device.

I know the dimenion of the tube.
I know how much is poured into the tube.
Due to regulations no sensors alowed in the setup.

I have to provide a "gauge" that tells the height of the product in the tube.

Since I know the amount of of product in the tube, I know the area of the circle segment.
Since I know the dimensions of the tube I know the radius.
Chord is unknown.

I wanted to calculate the height of the product. Present to the operator.
Not at a high accuracy.

For the "curiosity" ...the height is required since experienced has learned us that above and below a certain productheight the product is changed in homogeniousity.
This is to be avoided.
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July 1st, 2013, 11:39 PM   #8
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Re: Circle segment area

Well since you don't need high accuracy then it's easy to get a result using trial and error. Here is an approach. First calculate



Get a number for that. Then use the graph of

[attachment=0:1j832pdu]MSP2201f207geaebfh4f1800003f19938gg2h3h8c8.GIF[/attachment:1j832pdu]

That number you calculated? Locate it on the vertical axis , then move horizontally accross till you hit the graph , then drop vertically down to the horizontal axis and read the value. That is your and it is in RADIANS.

Confirm your work by substituting that value into the formula to see how accurate it is. Make sure your calculator is in RADIANS mode. Accuracy will depend on how well you have read the graph. If you can get to within 2 to 3 decimal places it may be adequate to use that value to calculate the height to within reason.

Post your calculations so that we may do them as well , in particular, post A and r.

Attached Images
File Type: gif MSP2201f207geaebfh4f1800003f19938gg2h3h8c8.GIF (3.4 KB, 222 views)
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July 2nd, 2013, 03:54 AM   #9
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Re: Circle segment area

Urgh..

I will need a sharp chisel to get this into a PLC.
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July 2nd, 2013, 08:52 AM   #10
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Re: Circle segment area

Well, why don't you go here:
http://www.ajdesigner.com/phpcircle/cir ... _theta.php

Easier that typing back and forth here

Another good place:
http://mathworld.wolfram.com/CircularSegment.html
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