ELLIPSES IN CYLINDERS

The section of a cylindrical surface whose plane is cut along its axis will always be an ellipse, the foci of which will be the tangent points of two tangential spheres to the cylinder and the plane. The sum of the distances from one point of the ellipse to the two foci is equal to the (constant!) distance between the equators of the spheres.

If the plane section of a right-angled cylinder is a circumference, what can we say about the plane?

Salomon's columns

Index

Ellipse, sinusoid & cylinder