Triangle and midpoint
Explain what You see. We recommend to use http://www.screencast-o-matic.com/ and talk over the video.
VIDEO: http://youtu.be/qaYhMJwxDfg
Share Your experience: https://docs.google.com/forms/d/1y8a_294oM_g1DWIC4Ze6vMuk6ivBq86YUVcAwiJA7v8/viewform