In this ten-minute video clip, Sal Khan, of Khan Academy, compares perpendicular bisectors to angle bisectors to medians to altitudes in this review. (09:56)

The instructor uses computer software to discuss vertical angles, exterior angles, alternate interior angles, etc. The sound quality could be a little better.

The instructor uses an electronic blackboard with different colors. The angle game is explained and played using a star shape. Using information student knows about various angles they can figure out the sizes of the angle X. Video can be stopped a...nd then restarted to get solution. Video gives some measurements and instructed to find the rest of the angles. This game and shape is definitely a challenge to students, but could be fun for students looking for extra practice on angle measurement. (9:49)[more]

In this TeacherTube video, the instructor shows how to find angle measurements. The writing on the instructors' white board is small, so viewers may want to open the video to 'full screen'. (04:12)

Sal Khan shows that the three medians of a triangle divide it into six smaller triangles of equal area. There is a brief discussion of the centroid as well. (07:46)

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