[b]Background[/b][br][i]GeoGebra [/i]has tool for easily constructing parallel lines and perpendicular lines.  In this activity you will use these tools to experiment with parallel and perpendicular.[br][br][b]Step 1.  The [i]GeoGebra [/i]Parallel Line Tool[/b][br]Now select the PARALLEL LINE tool [icon]/images/ggb/toolbar/mode_parallel.png[/icon].  Read the instructions for this tool: SELECT POINT AND PARALLEL LINE. So, before you can use this tool, you need a point and line.  [br]First make the line. Use the LINE tool [icon]/images/ggb/toolbar/mode_join.png[/icon] to create a line anywhere on the [i]GeoGebra [/i]page.  This line is Line AB. [br][br][i]GeoGebra[/i] now needs to know how far away from this line to draw the new parallel line.   Use the NEW POINT tool [icon]/images/ggb/toolbar/mode_point.png[/icon] to create a Point C somewhere near the Line AB.[br]Now select the PARALLEL LINE tool[icon]/images/ggb/toolbar/mode_parallel.png[/icon]. Click on Point C and then click anywhere on Line AB.  You have constructed a new line that is [color=#ff0000][b][i]parallel[/i][/b] [/color]to Line AB at Point C.[br][br][b]Step 2.  The [i]GeoGebra [/i]Parallel Line Tool[/b][br]Select the PERPENDICULAR LINE tool [icon]/images/ggb/toolbar/mode_orthogonal.png[/icon].  Read the instructions for this tool: SELECT POINT AND PERPENDICULAR LINE.[br][br]You already have points and lines on the page, so use those to test this tool.[br][br]Click on Point C and then click on Line AB.  The newly constructed line is [b][i][color=#ff0000]perpendicular [/color][/i][/b]to Line AB at Point C.[br][br][b]Step 3.  Experiment[/b][br]Use the MOVE tool [icon]/images/ggb/toolbar/mode_move.png[/icon] to grab and drag Point A, B, or C.  Observe the three lines [br]as you do this.  What do you notice?  [br][br]Once you have constructed parallel or perpendicular lines in [i]GeoGebra [/i]using these tools, they remain parallel or perpendicular even if you change their positions on the page.