Exploring 3D space with a computer - Part 2: a set of solids
Adrian Oldknow
In the first part of this guide we saw how a variety of basic tools could be used to build up a 3D model. These enable us to construct objects like the midpoint of a segment, or a line perpendicular to a plane. They also enable us to transform an object to give a new one, such as translating by a vector or reflecting in a plane.
There are three different types of reflective symmetry in Cabri 3D.
The drop down menu for transformations calls these: `Central Symmetry', `Half-Turn' and `Reflection'. The screen shot shows a triangular pyramid WXYZ with the face WYZ left open. Using `Central Symmetry' you can reflect each of the three triangular faces in the point A . Similarly, using `Half-Turn' you can reflect them in the segment BC . Finally you can reflect them in the plane through D,E,F . Use the working model below, or download the file
Symmetries.cg3
*See the effect of moving any of the points A,B,C,D,E,F or the vertices W,X,Y,Z .
* Once you have Cabri installed on your system, you will be able to see and interact with all of the examples displayed on this page.
To download and use the examples within the Cabri program itself, click links dislayed as: filename.cg3 etc.
