Side Splitter Theorem Investigation

Given: segment ED is parallel to segment AC.

What do you notice about the way the ED cuts the other two sides of the triangle? Click and drag point D, and/or any of the three vertices of triangle ABC to test your conjecture.

Try looking at the angles in the diagram.

How could you use these angles to prove your conjecture? You don't need to write a full 2-column proof (yet), but outline the steps you might use.