Double-click on the movie to PLAY.

Click once to PAUSE.

RELOAD the page to return to the START of the movie.


Here is a fuller and perhaps more illuminating version of the same rotation.

This also allows us to think about area: what we have here is the beginnings of a proof of Pythagoras' Theorem.

[We found this diagram in "Proof Without Words 2" by Roger B Nelson (2000), who attributes this proof to Leonardo da Vinci. And it was this diagram that led us to develop this whole activity.]