Move [icon]/images/ggb/toolbar/mode_move.png[/icon][br]Point [icon]/images/ggb/toolbar/mode_point.png[/icon][br]Plane Through 3 Points [icon]/images/ggb/toolbar/mode_planethreepoint.png[/icon][br]Intersect Two Surfaces [icon]/images/ggb/toolbar/mode_intersectioncurve.png[/icon][br][br][b][color=#1e84cc]In this introductory exercise, we'll learn a means through which students can discover the intersection of any 2 (non-parallel) planes. [/color][/b]

1) Select the POINT [icon]/images/ggb/toolbar/mode_point.png[/icon] tool. Use this tool to plot 3 points anywhere on the gray plane. [br][br]2) Select the MOVE [icon]/images/ggb/toolbar/mode_move.png[/icon] arrow. Click twice on any one of the points you plotted in step (1).Use this tool to [br] move this point off of the gray plane. Repeat this process for the other 2 points. [br][br]3) Select the PLANE THROUGH 3 POINTS [icon]/images/ggb/toolbar/mode_planethreepoint.png[/icon] tool. With this tool highlighted, select the 3 points you [br] initially plotted in step (1). This will create a plane that passes through these 3 points. [br] [b] [br] Note:[/b] This step could have also been done without plotting the points first (step 1).[br] Steps (1) - (2) were included here simply to acquaint you with plotting & moving points in 3D. [br][br][b][i]Further directions appear below this applet. [/i][/b]

4) Select the MOVE [icon]https://www.geogebra.org/images/ggb/toolbar/mode_move.png[/icon] arrow. Use this tool to drag any one (or more) of these 3 points around. Notice [br] how the plane you plotted in (3) always passes through these 3 points. [br][br]5) Now select the INTERSECT 2 SURFACES [icon]https://www.geogebra.org/images/ggb/toolbar/mode_intersectioncurve.png[/icon] tool. Select the plane you plotted in step (3). Then select [br] the gray plane. This will now plot the intersection of these 2 surfaces (here, planes).

[color=#0000ff]When you're done (or if you're unsure of something), feel free to check by watching the quick silent screencast below the applet.[/color]