Can you Find the Focal points of an Ellipse?

[Acorn]

Using the Xara ellipse too, create a Red ellipse of width (major axis) 400px and height (minor axis) 200px.



The Challenge is to find the focal points F1 & F2 without any calculation.

Your "proof" will be any triangle with a base of F1F2 (346.4px) and apex on the rim of the ellipse will have a Perimeter of 746.4px.

P(F1AF2) = P(F1BF2) = P(F1CF2).

Knowing the length between the focal points and with a rope or twine the length of the perimeter and tied into a single loop, it would be possible to inscribe the ellipse to be the basis of an elliptical pond or garden feature.

The path from one focus to the rim to the other focus is always goings to be 400px.
This is the reason whispering galleries work; any sound made at either focus is concentrated at the other one.

Acorn