# G.GCO.7 SAS: Dynamic Proof!

- Author:
- Dan Dale, Tim Brzezinski

- Topic:
- Congruence, Triangles

The

**states that**__SAS Triangle Congruence Theorem__**if 2 sides and their included angle of one triangle are congruent to 2 sides and their included angle of another triangle, then those triangles are congruent.**The applet below uses transformational geometry to dynamically prove this very theorem. Interact with this applet below for a few minutes, then answer the questions that follow. As you do, feel free to move the**BIG WHITE POINTS**anywhere you'd like on the screen!**Questions:**1) What geometry transformations did you observe in the applet above? List them. 2) What common trait do all these transformations (you listed in your response to (1)) have? 3) Go to this link and complete the first 5 exercises in this GeoGebra Book chapter.