Me
Posts:
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Registered:
1/23/16


Re: How we get a Ellipse from a Conic, and how we get a Oval from Cylinder Sections knifes that are V and asymmetrical V shaped
Posted:
Oct 5, 2017 5:47 PM


On Thursday, October 5, 2017 at 10:11:12 PM UTC+2, Dan Christensen wrote:
> Archie, for $52.49, you can save yourself all this embarrassment. Order the > "Conic Sections Model" made of transparent plastic. See for yourself  no > knives or scissors required  that at an ellipse is indeed a conic section.
Actually, he could save some money by trying to understand a simple proof/demonstration (the core of which is consisting of just 3 lines!):
...
From r(x) = a  ((ab)/h)x and d(x) = a  ((a+b)/h)x we get that y(x)^2 = = r(x)^2  d(x)^2 = ab  ab(2x/h  1)^2 = ab(1  4(x  h/2)^2/h^2. Hence (1/ab)y(x)^2 + (4/h^2)(x  h/2)^2 = 1, which is the equation of an ellipse.

