Cinderella applets

Fun with Cinderella

Cinderella is a commercially available 2-D geometry drawing program, very well suited to demonstrate geometrical principles and constructions. I use it to make JAVA applets to convey geometric algebra (even though it is not written in that language!) and useful constructions for Lego hobbyists.

The first demo you start will take some time, since it needs to download the 421 kb jar-file containing the cinderella code that runs all examples. All demos after that will start much more quickly.

Geometric algebra - specific
- line representation, by 2-blades (bivectors)
- intersection of lines, in 2-space
- separation of skew lines, by trivectors
- rotation composition , by multiplication of quaternions, visualized on the sphere of directions
- projection using a pinhole camera
- inverse of a vector
- inverse of a bivector
- projection onto a rotor
- composition of projections
- Eckhard Hitzer has many more Cinderella/GA demos in the same vein.
Fun geometry
- 5-circle theorem, and a nice little pentagon puzzle
- Simson's theorem, about the special nature of a circumcircle
- touching-circle theorem, using inversive geometry
- Snell's law, by construction.
Linkages
- 4-bar linkage, the primal linkage
- 8-bar linkage, how to get a piano on stage
- dwell mechanism
- Peaucellier cell, to convert between rotary and linear motion
- walking beams, how to power a Norwegian mine on top of a mountain using water at the bottom

Leo Dorst 20020626