GeoGebra 3D Beginner Tutorial: Exercise 1

NEW TOOLS WE WILL LEARN HOW TO USE:
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]
DIRECTIONS:
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).
QUESTION:
What can we conclude about the intersection of any 2 non-parallel 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]
Quick (Silent) Demo

4 Ways to Quickly and Easily Construct an Equilateral Triangle With Vertices on Both xAxis and zAxis

Final Product:
Method 1: Simply plot 2 points on the xAxis. Then use Pythagorean Theorem to determine coordinates of 3rd vertex on zAxis.
Method 2: Use the REGULAR POLYGON tool to build directly on gray coordinate plane. Then rotate everything 90 degrees about the xAxis.
Method 3: Compass and straightedge constructions in MIDAIR? Absolutely! Here, we simply use the CIRCLE WITH CENTER THROUGH POINT tool twice. Note how we need to specify an axis of the circle as well (since we are in 3D).
Method 4: Use the ROTATE tool to rotate one point on the xAxis 60 degrees about the other point.

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