Geometric Constructions - Triangles - Math -Interactive GeoGebra Applet

Incorporate technology in your class and let GeoGebra be your key partner in the learning process.

This applet uses a virtual straightedge (in centimeters and inches), a virtual protractor and virtual pairs of compasses to simulate some basic geometric constructions that students are required to do on the paper. I tried to make the tools as realistic as possible (especially the protractor and the straightedge)

.

The straightedge draws up to 4 segments, the protractor draws up to 3 angles and there are 4 pairs of compasses in use. The main focus is on exploring whether a triangle can be constructed with the above tools when three measures of sides or angles are given and whether this can be done in a unique way. Some cases to be checked could be:

a) All three side are known (SSS).

b) All three angles are known (AAA).

c) Two sides and the included angle are known (SAS).

d) Two angles and the included side are known (ASA).

e) Two angles and a non-included side are known (AAS).

f) Two sides and a non-included angle are known (SSA) (The triangle is not uniquely constructed).

Apart from dealing with the triangles, you may also want to experiment with some other geometric constructions such as:

a) Bisecting a given angle.

b) Drawing the perpendicular bisector of a given segment.

c) Constructing an isosceles or equilateral triangle.

d) Constructing a parallelogram when two sides and the included angle are given.

and maybe with a few more.

This description is also included in the product as a printable word document.

I have also put together a preview video so that you will be able to get an idea on how these virtual tools work. In its two-minute time, (this is the limit for making preview videos), I show how the protractor is used and how an SSS (6,5,4) triangle is constructed with straightedge and compass.

To be able to see and play with the applet you will need to download and install the free software GeoGebra in your computer or tablet if you haven’t done this before. The process is very simple and quick: The link is

https://www.geogebra.org/download

from which you can download GeoGebra Classic 5 (this is the version that I also use).