[b]Step 1.  Construct[/b][br]One the [i]GeoGebra [/i]page you will see four geometric objects:[br]1. Point A[br]2. Point B[br]3. Point C[br]4. Line BC[br]On the Tool Bar there is a PERPENDICULAR LINE tool [icon]/images/ggb/toolbar/mode_orthogonal.png[/icon].Click on the PERPENDICULAR LINE tool to select it.  Notice the instructions for this [i]GeoGebra [/i]tool: Click first on Point A and then click on Line BC.  This will create a new, perpendicular line.  But just what is a “perpendicular line?”[br][br][b]Step 2.  Experiment[/b][br]Use the MOVE tool [icon]/images/ggb/toolbar/mode_move.png[/icon] to experiment by moving Points A, B, or C. Move the two lines as well. Make observations. If needed, use the ZOOM IN [icon]/images/ggb/toolbar/mode_zoomin.png[/icon]or ZOOM OUT tool [icon]/images/ggb/toolbar/mode_zoomout.png[/icon] to change your view.[br][br][b]Step 3. New Construction[/b][br]Use the DELETE OBJECT tool [icon]/images/ggb/toolbar/mode_delete.png[/icon] to click on all the points and lines on the [i]GeoGebra [/i]page and delete them. Now use the NEW POINT tool [icon]/images/ggb/toolbar/mode_point.png[/icon], the LINE THROUGH TWO POINTS tool [icon]/images/ggb/toolbar/mode_join.png[/icon], and the PERPENDICULAR LINE tool [icon]/images/ggb/toolbar/mode_orthogonal.png[/icon] to create your own perpendicular lines and again experiment by moving points or lines.[br][br][b]Step 4. Conclusions[/b][br]So just what is a perpendicular line?  Share your conclusions with your teacher.