Double-click on the movie to PLAY.

Click once to PAUSE.

RELOAD the page or double-click to return to the START of the movie.


Here ABCD and its image are extended one line segment at a time, until the latest endpoint of the object and image meet (at a point X, the centre of rotation).

This process could go on for a long time. In the above example, the zig-zag ends up with a total of 9 segments (four more than zig-zag ABCDEF in the original task).

the end