Re: [math-fun] conic sections

On Nov 8, 2018, at 10:06 AM, Mike Speciner <ms@alum.mit.edu> wrote:

And the focus to focus reflection of ellipses is easy to see when using the constant sum of distances to foci property.

I guess I need to sketch a proof that at each point x on the ellipse, the curve is perpendicular to the bisector of the lines connecting x to the two foci. C