Reduction and Enlargement

This applet shows the enlargement/reduction of a triangle with scale factor k and center O.




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)


Here are several of the activities that the teacher/student can do:

• The teacher may hide some elements in the objects (using the check box), and let the students predict the position of the missing objects.
• The students may use the distance, area and angle tools to investigate the relationship between the two triangles. 

Click here to download applet.

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.