We consider several seemingly unrelated theorems, each with the word ellipse in the statement: Siebeck’s theorem, the elliptical range theorem, Poncelet’s theorem, and the Blaschke ellipse theorem.

I have very fond memories of high school geometry. Memorizing theorems wasn't too hard, and solving proofs was like solving the logic puzzles that I did for fun anyway. But the theorems were scattered ...

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory. She reports on topics from maths and history to society and animals. Katie has a PhD in maths, ...