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Re: My third proof ellipse is never a conic is that the tip end of cone and bottom flared-out end can never yield a 1000to1 ellipse

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Alan Mackenzie <acm@muc.de> writes:

>Archimedes Plutonium <plutonium.archimedes@gmail.com> wrote:
>> On Saturday, January 5, 2019 at 2:13:53 PM UTC-6, Peter Percival wrote:

>>> 
>>> The OP may like to look up "spheres of Dandelin".  This 
>>> https://en.wikipedia.org/wiki/Dandelin_spheres, for example, has a nice 
>>> picture.
>>> 

>> Hi, Peter, I am hoping OP does not mean me. 

>No, "OP" means "original poster", and that is definitely not you.

He is refering to me.

>> For my third proof that the ellipse is never a conic, is simple.

>It may be simple, but it is not a proof, and it is wrong.

>> Get three figures and elongate.

>> So you have a ellipse that elongates from 10to1, to 100to1 to 1000to1
>> etc etc A cylinder that elongates from 10to1radius, to 100to1radius to
>> 1000to1 radius etc etc

>> Now, finally you elongate a cone in 10to1radius to 100to1radius, etc
>> etc.

>WTF does this mean?  10to1radius?

He seems to mean semimajor axis and semiminor axis.

>> Notice that as you elongate a ellipse and a cylinder, they are
>> symmetrical from side to side and from top to bottom. And you can fit
>> the ellipse inside the cylinder and make a cut to get the ellipse

>Yes.

>> But notice as you elongate a cone, you always have a sharp tip top and
>> a flaring-out at the bottom. In other words, no ellipse comes out of a
>> cone.

>Wrong.  The "flaring-out" you envisage at the bottom is compensated for
>by the sharper angle at which the section plane meets the cone at the
>bottom, giving an ellipse, symmetrical in two axes.

>> Simple proof.

>Simple, yes, but proof, no.  It's what happens when you try to use
>intuition in place of sound mathematics.

Yes it's no proof since there is no formula or anything to demonstrate
how the curve responds as it moves down the cone. Others have, and have
shown the resulting formula matches that of an ellipse.

>I seriously recommend you to seek out a photograph of a sectioned cone.
>You will see that it is symmetrical in two axes.  Even better, make
>yourself a cone out of clay, or butter, or whatever, and cut it
>yourself.  You will see the ellipse, and hopefully then spare us all
>this nonsense on sci.math.

He has already done stuff like that. He apparently made a paper cone,
placed a (circular) Mason jar lid in it at an angle, saw it didn't fit
well, and declared that this "proves" an ellipse is not a conic section.
No, it demonstrates that an angled cut is not a *circle*.

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AP's thoughts as of 5JAN2019// three proofs that ellipse is never a conic Archimedes Plutonium <plutonium.archimedes@gmail.com> - 2019-01-05 07:19 -0800
  Legitimate geometry question on cone-plane intersection moroney@world.std.spaamtrap.com (Michael Moroney) - 2019-01-05 17:48 +0000
    Re: Legitimate geometry question on cone-plane intersection Alan Mackenzie <acm@muc.de> - 2019-01-05 18:58 +0000
      Re: Legitimate geometry question on cone-plane intersection moroney@world.std.spaamtrap.com (Michael Moroney) - 2019-01-05 19:44 +0000
        Re: Legitimate geometry question on cone-plane intersection Peter Percival <peterxpercival@hotmail.com> - 2019-01-05 20:15 +0000
        Re: Legitimate geometry question on cone-plane intersection Alan Mackenzie <acm@muc.de> - 2019-01-07 03:15 +0000
          Re: Legitimate geometry question on cone-plane intersection moroney@world.std.spaamtrap.com (Michael Moroney) - 2019-01-07 04:44 +0000
      Re: Legitimate geometry question on cone-plane intersection Peter Percival <peterxpercival@hotmail.com> - 2019-01-05 20:13 +0000
        My third proof ellipse is never a conic is that the tip end of cone and bottom flared-out end can never yield a 1000to1 ellipse Archimedes Plutonium <plutonium.archimedes@gmail.com> - 2019-01-05 13:44 -0800
          try wrapping a ellipse in a cone wrapper Re: My third proof ellipse is never a conic is that the tip end of cone and bottom flared-out end can never yield a 1000to1 ellipse Archimedes Plutonium <plutonium.archimedes@gmail.com> - 2019-01-05 14:24 -0800
            Re: try wrapping a ellipse in a cone wrapper Re: My third proof ellipse is never a conic is that the tip end of cone and bottom flared-out end can never yield a 1000to1 ellipse Archimedes Plutonium <plutonium.archimedes@gmail.com> - 2019-01-05 14:40 -0800
              researching if the ellipse has an internal universal constant of 1/137 Archimedes Plutonium <plutonium.archimedes@gmail.com> - 2019-01-05 17:37 -0800
                researching if the ellipse has an internal universal constant of 1/137 Archimedes Plutonium <plutonium.archimedes@gmail.com> - 2019-01-05 21:13 -0800
                Re: Archimedes "Village Idiot" Plutonium flunked the Math Test of a lifetime-generation test moroney@world.std.spaamtrap.com (Michael Moroney) - 2019-01-06 05:55 +0000
                not even a constant percentage in the rectangles Re: researching if the ellipse has an internal universal constant of 1/137 Archimedes Plutonium <plutonium.archimedes@gmail.com> - 2019-01-05 21:59 -0800
                no percentage formula Re: researching if the ellipse has an internal universal constant of 1/137 Archimedes Plutonium <plutonium.archimedes@gmail.com> - 2019-01-05 22:14 -0800
                not even rectangles Re: no percentage formula Re: researching if the ellipse has an internal universal constant of 1/137 Archimedes Plutonium <plutonium.archimedes@gmail.com> - 2019-01-05 23:02 -0800
                directrix Re: not even rectangles Re: no percentage formula Re: researching if the ellipse has an internal universal constant of 1/137 Archimedes Plutonium <plutonium.archimedes@gmail.com> - 2019-01-05 23:34 -0800
                understanding the Ellipse well,is the same as understanding angular momentum of physics well Archimedes Plutonium <plutonium.archimedes@gmail.com> - 2019-01-05 23:51 -0800
                Re: understanding the Ellipse well,is the same as understanding angular momentum of physics well Me <franz.fritschee.ff@gmail.com> - 2019-01-06 03:10 -0800
          Re: My third proof ellipse is never a conic is that the tip end of cone and bottom flared-out end can never yield a 1000to1 ellipse Me <franz.fritschee.ff@gmail.com> - 2019-01-06 03:08 -0800
          Re: My third proof ellipse is never a conic is that the tip end of cone and bottom flared-out end can never yield a 1000to1 ellipse Alan Mackenzie <acm@muc.de> - 2019-01-06 11:17 +0000
            Re: My third proof ellipse is never a conic is that the tip end of cone and bottom flared-out end can never yield a 1000to1 ellipse moroney@world.std.spaamtrap.com (Michael Moroney) - 2019-01-06 18:42 +0000
  Re: AP's thoughts as of 5JAN2019// three proofs that ellipse is never a conic Jan <filmart@gmail.com> - 2019-01-06 21:47 -0800

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