Tools

Change the slider to zoom in.

Manage the tool bar

You can customise the tool bar that is shown in GeoGebra. This is handy if you want to make a ruler-compass-construction. Restricting the number of tools, can also be used as a help for the students.

You customise the tool bar under the menu Tools->Customise toolbar...

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This window is also used for restoring the default toolbar.

Create a Tool!

You can create your own tools in GeoGebra. This is a useful feature if you need to do the same operation several times.

  • Start by creating your construction
  • Choose Tools->Create New Tool...
  • Under the tab Output Objects you choose the objects your tool should create. These objects are the result of your tool. Click Next
  • Under the tab Input Objects you choose the objects needed to create the result. Click Next
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  • Name your tool and click Finish

The Sierpinski triangle

The recording below shows how to create a tool to make a Sierpinski triangle.

Pattern of pentagrams

Construct a pentagram as shown on the page GeoGebra Tutorial - Constructions.

When making a repetetive pattern, the final construction will contain very many objects. In order to minimize the number of objects, one can make tools that only produce the objects needed to continue the pattern.

Start by making a tool that produces a pentagram and all its vertices. In the picture below, the pentagram-polygon and the points C to J will be the output objects. The points A and B will be the input objects.

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Use the tool created to make a pentagram, and then another pentagram inside the first one. Hide the largest pentagram, it will not be needed in next tool.

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Make a repetetive pattern as in the picture below. The only points that are needed to continue the pattern, are two of the innermost vertices, e.g. the points N and O. Make a new tool that produces all the polygons, except the hidden one, and also produces the points N and O.

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Use the tool created to make a repetetive pattern.

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Using a slider to zoom

If zooming to the origin, the centroid of the pattern must be placed at the origin. Let the initial point A have the value (100cos(pi/10), 100sin(pi/10)), and let the other initial point B have the value (0,100).

The ZoomIn command can be used either by specifying a scale factor, or by specifying the minimum and maximum of the x and y-axes:

ZoomIn[ <Min-x>, <Min-y>, <Max-x>, <Max-y> ]. 

Enter a slider n. Open the properties window and choose the Scripting tag for the slider n. Enter the GeoGebra script:

ZoomIn[-75*0.981^n,-75*0.981^n,75*0.981^n,75*0.981^n]

This zoom will use a scalefactor of 0.981 in each step. Adjust the window to make it a square.

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further info:

Pascal's Tree for kids: http://splashscuola.altervista.org/esercizi/geogebra/5-frattali_casette01.shtml

 

by Malin Christersson under a Creative Commons Attribution-Noncommercial-Share Alike 2.5 Sweden License

www.malinc.se