Triangle Angle Sum Proof 2

1.) Move the vertices of the triangle to determine the shape and size of the triangle you want.
2.) Move the slider to the extreme right. What do you observe?
3.) What is the relationship between the three angles which meet at a point, and the three interior angles of a triangle?
4.) What can you say about the angle sum of the parallelograms/trapezium formed?
5.) Make a conjecture about your observation.

Sorry, the GeoGebra Applet could not be started. Please make sure that Java 1.4.2 (or later) is installed and active in your browser (Click here to install Java now)

Another demonstration that shows that the sum of the interior angle of a triangle is 180°.

Triangle Angle Sum Proof

Move the vertices of the triangle and move sliders P and Q to the extreme right. What do you observe?




















This is a Java Applet created using GeoGebra from www.geogebra.org - it looks like you don't have Java installed, please go to www.java.com


Based on your observations, make a conjecture about the angle sum of a triangle.

There is a tutorial here on how to create the applet above.