Drag the vertices of triangle ABC so that it is similar to triangle DEF.
Note the given side lengths. What can you do with this information? Discuss with your group, and investigate the relationship between the triangles with respect to the given side lengths.
Discuss all of the observations you made about the parts of the similar triangles. Ask yourself this: what must be known about a set of triangles in order to argue in favor of their similarity? There are a few possibilities. See if you can come up with three different arguments for three different relationships (i.e.: relating sides, angles, sides and angles...) and discuss them with your group.
Think back to our conversation about uniqueness of triangles, when we were first visiting triangle congruence. What more can you add to your argument(s)?