With the fast-pace advancement of technology, computers in particular, we teachers need to cope up and exploit these technologies and integrate them in teaching. In mathematics, commercial software have been developed commercially for the last three decades, but recently, more and more free software were developed, and the source codes were even made public. This open-source method helped software to be developed by programmers from different places around the world.

To give you an idea of what GeoGebra can do, I have created some applets below for you to explore. The first applet shows that the angle sum of a traingle is 180 degrees, the second shows the effects of the parameters *a *and *b* in the linear function *y = ax + b*, and the third shows the concept of Riemann sums.

**Note: **If the applets do not display in your computer, you have to download and install the Java Runtime Environment to run it.

**Triangle Angle Sum**

*Drag A,B,C to choose shape, and then drag the circle on slider t to extreme right to rotate the triangle.*

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)

**Linear Function**

*Drag the circles on sliders a and b and investigate the effect of their values to appearance of the graph*

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)

**Riemann Sums**

*Drag the circle in slider n to investigate the sum of the area of the rectangles.*

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)

**GeoGebra Step-by-Step Tutorials**

*Guillermo Bautista is a mathematics teacher from the Philippines. He, together with Erlina Ronda, established the first GeoGebra institute in the Philippines, the GeoGebra Insitute of Metro Manila. His academic blogs are Math and Multimedia and GeoGebra Applet Central.*