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GeoGebraGeoGebra Classroom

GoGeometry Action 101 !

Creation of this applet was inspired by a tweet from Antonio Gutierrez (GoGeometry). You can control the size of the interior angle with green vertex by using the green slider. Also, feel free to move any of the triangle's vertices anywhere you'd like at any time. Why is the phenomenon (seen at the end) always true? How can we formally prove this true?

Quick (Silent) Demo