Triangle Angle Sum Theorem (Visual Proof) High School Geometry

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This is a flipped classroom video I made for high school geometry students. It is a visual proof that the measures of the angles of a triangle add up to 180 degrees. No matter what triangle is used for the demonstration, the result will always be the same. There are practice problems at the end of the video.

This is something I did not learn how to do until college, but it engages students and is super easy! I was introduced to this as a proof, although some people may argue that it is not since it would have to be demonstrated for every single triangle ever.

So, if this proof does not suffice for you, there are several others.

If you would like to check validity, you may reference these:
  1. Lacey Surak
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