Folding Conics

Bruce Yoshiwara
Los Angeles Pierce College
6201 Winnetka Avenue, Woodland Hills, CA 91371
e-mail: byoshiwara@hotmail.com or yoshiwbw@piercecollege.edu
http://www.piercecollege.edu/faculty/yoshibw/talks/amatyc05/

Abstract: By making appropriate simple creases in a piece of (“patty”) paper, we can create excellent approximations to parabolas, ellipses, and hyperbolas. Locus of points descriptions of the conics explain why the folding works, and the folding activity also leads to a calculus-free derivation of the reflection properties of the conics. Applications of the reflection properties are given, as well as Geometer’s Sketchpad files (with instructions) to illustrate the conics produced by paper folding.