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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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A Planar Geometry Problem
First: in general, it is not solvable. There are points which cannot
lie on a circle tangent to two others. E.g., the point cannot be inside either circle. And there are 4 other, "small", areas that are difficult to describe, but are easily shown on a graphic (later). Second, and more importantly, the radius of the solution circle can approach infinity. So, in practical terms, it becomes unsolvable at some point, depending upon whether you are using CAD or a drawing board G. Now, there are three cases for the solution: where the given circles are externally or internally tangent to the solution circle, or one of each. Do your problems always fall into one of these classes? Also, if the given circles can overlap, it may be a different set of solution classes (I haven't thought that through). Do your circles ever overlap? I love plane geometry, Bob |
#2
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A Planar Geometry Problem
On 05/03/2011 02:44 PM, Bob Engelhardt wrote:
First: in general, it is not solvable. There are points which cannot lie on a circle tangent to two others. E.g., the point cannot be inside either circle. And there are 4 other, "small", areas that are difficult to describe, but are easily shown on a graphic (later). Second, and more importantly, the radius of the solution circle can approach infinity. So, in practical terms, it becomes unsolvable at some point, depending upon whether you are using CAD or a drawing board G. Now, there are three cases for the solution: where the given circles are externally or internally tangent to the solution circle, or one of each. Do your problems always fall into one of these classes? Also, if the given circles can overlap, it may be a different set of solution classes (I haven't thought that through). Do your circles ever overlap? I love plane geometry, I generally love plane geometry, but this has me stumped -- at least as a compass-and-straightedge problem. The immediate problem is for making pseudo-ellipsis in a cheap CAD program (Qcad), so one could even restrict the two 'master' circles to being the same diameter. But there are times when I'd like to use different sized circles for this (imagine a triangle with rounded corners, and 'puffy cheeks'). I can see an algebraic approach for this involving over use of the Pythagorean theorem, but I'd rather know if there's a solution that can be done by construction, not by numbers. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html |
#3
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A Planar Geometry Problem
Here's a method for drawing a pseudo ellipse using a cheap CAD program,
or compass and straight edge. http://tinyurl.com/yejlsy3 -- Regards, Gary Wooding (To reply by email, change gug to goog in my address) Tim Wescott wrote: ...snip The immediate problem is for making pseudo-ellipsis in a cheap CAD program (Qcad), so one could even restrict the two 'master' circles to being the same diameter. But there are times when I'd like to use different sized circles for this (imagine a triangle with rounded corners, and 'puffy cheeks'). |
#4
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A Planar Geometry Problem
Can you post a picture?
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