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.

In this movie, the side AB again increases until it is 11 units long, and then decreases down to 0. As AB decreases the movie pauses at various salient points to help students think about the relationship between AB (and AD) and the size of the square EFGH. You can of course pause the movie indefinitely at these points.

Students might notice, for example, that the shorter AB becomes, the closer E gets to AB (and G gets to DC, and so the longer EG becomes).

They might also realise that the square has the same area as a rectangle with base EG and with height half of HF (ie Area = 0.5xEGxEG).

In the movie on the next page we keep AB fixed but change the length of AD.