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.

**PS**

Here is a way of showing that our first conjecture (Method A) is false,

ie it is NOT the case that DA bisects the angle at A when D is the midpoint of BC.

ie it is NOT the case that DA bisects the angle at A when D is the midpoint of BC.

Here F is a point such that AF = AB (ie ABF is isosceles).

So, if DA does bisect the angle at A, then E will be a midpoint of BF.

But if E and D are both midpoints, then ED must be parallel to FC,

which means ED produced will not go through A...

You might be able to find a better way of formulating an argument based on this situation ...

The end