IM Geo.1.8 Lesson: Using Technology for Constructions

Author:GeoGebra Classroom Activities, IM Algebra 1, Geometry, Algebra 2

Use the Constructions App.

Try all the tools in the workspace.

Find the Undo button. Click on the image of 3 stacked segments, the Main Menu, to save your work or go to a new page. Which tools do the same work as a straightedge?

The Constructions App has 3 tools to make a point. To learn about them, use the applet. In this applet, all 3 point tools have been used.

(or open the applet at ggbm.at/cuupdskk). Drag each point and each line around to see what happens in the Graphics View on the right. Look at the way the points are defined in the Algebra View on the left. Explain how each definition is related to the behavior of the corresponding point .

There are several ways to use the compass tool. Use the applet below.

First, set up a workspace that looks something like the image:

Draw circle through point .
Draw segment not intersecting the circle centered at .
Draw point not intersecting the circle centered at or segment .

Select the compass tool and then click on segment

. What happens?

Now click on the point . What happens?

Make a new segment that is the same length as . Make a circle with the same radius as the circle centered at . Explain how the digital compass tool is the same and how it is different from a physical compass.

Use the applet to create one or more of these figures:

a perpendicular bisector of line segment
an equilateral triangle
a regular hexagon
a square
a square inscribed in a circle
two congruent, right triangles that do not share a side

In order for your construction to be successful, it has to be impossible to mess it up by dragging a point. Make sure to test your constructions.

When you use the GeoGebra Geometry App below, you’ll see some basic tools.

(You can also go to geogebra.org/geometry) Click on the word “MORE” and you’ll see some categories of tools, including “Construct” tools.

perpendicular line tool	parallel line tool

Construct a line or a line segment and an additional point that is not on it. Then try the perpendicular line tool and the parallel line tool. Use the move tool to drag some points around, and observe what happens.
Use any of the digital tools to create one or more of these figures. Test your constructions by dragging a point.

	parallelogram
	rectangle
	rhombus
	square