posted
I never took advanced math classes and need to find the circumference of a 120" X 80" oval. Formula I got is: circumference = 2*pi*sqrt[(1/2)(a^2 + b^2)]. I came up with 640.76" Is this close (enough for government work)? I know this is not correct since a rectangle would be 400" where'd I go wrong?
-------------------- Bob Gilliland InKnowVative Communications Harrisburg PA, USA
"The U.S. Constitution doesn't guarantee happiness, only the pursuit of it. You have to catch up with it yourself." Benjamin Franklin Posts: 642 | From: Harrisburg, PA, USA | Registered: Nov 1998
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There are a few out there and depending which is used, various results are revealed. This is due in part to calculating and taking the elliptic integral into consideration. The “simple” formula that I’m aware of is 2 * pi * sqrt((a^2+b^2)/2), or what Ben said.
A more advanced formula: C = 2\pi a \left[{1 - \left({1\over 2}\right)^2\varepsilon^2 - \left({1\cdot 3\over 2\cdot 4}\right)^2{\varepsilon^4\over 3} - \left({1\cdot 3\cdot 5\over 2\cdot 4\cdot 6}\right)^2{\varepsilon^6\over5} - \dots}\right]
Or the method I used to get 317.355"; inside Omega, Shape>Distance Around Objects.
-------------------- Bob Gilliland InKnowVative Communications Harrisburg PA, USA
"The U.S. Constitution doesn't guarantee happiness, only the pursuit of it. You have to catch up with it yourself." Benjamin Franklin Posts: 642 | From: Harrisburg, PA, USA | Registered: Nov 1998
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posted
Darcy, I find that in the older versions of Flexi also. Edit/Job info/Statistics, and it gives the cut length. Wish it would give the area though.
Calculating area is something I spend too much time messing with when I need to take irregular shapes and max them out at say six square feet to meet a city code.
-------------------- The SignShop Mendocino, California
Making the simple complicated is commonplace; making the complicated simple, awesomely simple, that's creativity. — Charles Mingus Posts: 6716 | From: Mendocino, CA. USA | Registered: Nov 1998
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Speaking of area..... I need to find that also to figure material for this bid... Any help you math geniuses out there??? I searched online and couldn't find a formula which made sense to me.Rick I tried to get more bang for the area by using irregular shapes but here they go from outer dimensions instead of deducting negative space.
posted
Area of an ellipse would be pi* a * b, where a and b are half the distance of the minor and major axes (as reminded from further above).
Using that equation with your values; 3.14*40*60=7536, or if using the equation of pi*40*60 typed into Google as suggested by Jon, 7539.82237.
Inside Omega, making an ellipse sized to 80” x 120”, Shape>Area of Object reveals 7541.933 sqin, or 52.375 sqft.
-------------------- Bob Gilliland InKnowVative Communications Harrisburg PA, USA
"The U.S. Constitution doesn't guarantee happiness, only the pursuit of it. You have to catch up with it yourself." Benjamin Franklin Posts: 642 | From: Harrisburg, PA, USA | Registered: Nov 1998
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posted
The circumference of an oval? Easy. Cut out the oval. Put a mark on the edge and a matching mark on the ground. Roll your oval until the mark comes back around to land on the ground. Mark the ground at that spot. Measure the distance between the two ground marks with a tape measure. That's your circumference.
Hey, whaddya expect? I was never any good with calculus, but I can use a tape measure.
-------------------- "A wise man concerns himself with the truth, not with what people believe." - Aristotle
Cam Bortz Finest Kind Signs Pondside Iron works 256 S. Broad St. Pawcatuck, Ct. 06379 "Award winning Signs since 1988" Posts: 3051 | From: Pawcatuck,Connecticut USA | Registered: Nov 1998
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Cam gotcha, you can also use a measuring wheel or rope. but... I haven't built it ... just figuring for smalt bkgrd and gold leaf.Need to bid this before I get it or build it.
-------------------- Darcy Baker Darcy's Signs Eureka Springs. AR. Posts: 1169 | From: Eureka Springs, AR | Registered: Nov 2007
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Hey Darcy, You can get in the ballpark by figuring the area of a rectangle 120 X 80 inches. Draw it to scale. Now do a drawing of your oval inside the rectangle, with the arcs of the oval just touching the sides of the rectangle. Now draw a diagonal line across each of the 4 corner areas so it just touches the oval and joins the horizontal and vertical lines. You should have 4 right triangles of the same size. Figure the area of each ( I think it's 1/2b X h) and subtract from the total area of the rectangle.
Should get you pretty close, in a backyard kinda way.
-------------------- Dale Feicke Grafix 714 East St. Mendenhall, MS 39114
"I can do all things through Christ, who strengthens me." Posts: 2963 | From: Mendenhall, MS | Registered: Apr 1999
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I'm with you Deb. I'll bake them a pie but don't ask me to do more than balance my checkbook.
-------------------- Kimberly Zanetti Purcell www.amethystProductivity.com Folsom, CA email: Kimberly@AmethystProductivity.com
“Organizing is what you do before you do something, so that when you do it, it is not all mixed up.” AA Milne Posts: 3722 | From: Folsom, CA | Registered: Dec 2001
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317.355"
There are a few out there and depending which is used, various results are revealed. This is due in part to calculating and taking the elliptic integral into consideration. The “simple” formula that I’m aware of is 2 * pi * sqrt((a^2+b^2)/2), or what Ben said.
A more advanced formula: C = 2\pi a \left[{1 - \left({1\over 2}\right)^2\varepsilon^2 - \left({1\cdot 3\over 2\cdot 4}\right)^2{\varepsilon^4\over 3} - \left({1\cdot 3\cdot 5\over 2\cdot 4\cdot 6}\right)^2{\varepsilon^6\over5} - \dots}\right] 
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