Re: ATM (no subject)

[Stephen Tonkin <sft@aegis1.demon.co.uk>]

"Fred Maxwell - No spam e-mail accepted." <fmaxwell@erols.com> writes:
>Well, I for one, fell that it's about time we start demanding that
>telescope manufactuers produce egg-shaped diagonals.  When you think
>about it, that's the shape you get when you cut a cone at a 45 degree
>angle.

No it isn't.

Any section of a cone is, unsurprisingly, a conic section.  In the
context you are talking about, it is an ellipse. Other possibilities are
parabola, hyperbolae, circle -- and the degenerate cases of intersecting
straight lines, straight line and point.

The "egg-shape" is not a conic section.


--
Best,
Stephen