This handy sized template has a large version of Chris Tisdell's geometry tool, the TGT plus an arc sector template of matching 50mm radius, and a Neusis straight edge.
The Constructor One template can be an extension for the Mathomat template, or used on its own or in class sets for school.
Replacing the compass
The TGT was conceived by Chris Tisdell as a replacement for compass and straight edge construction in geometry classrooms. The practical problems with compasses in school are well known. They are difficult for students to control, resulting in slipping and distorted drawings. Compasses can be dangerous because of their steel points, and often they are very limited in the size of the radius they can draw. The compass and straight edge also, are separate unintegrated tools that students need to remember to carry with them.
What is less well known is that a TGT, with its fixed 25mm radius used in conjunction with the straight edge side of the Mathomat template it is in can be used to perform all of the common high school constructions in high school curricula. You can read abut the development of this theorem by Francesco Severi in Chris Tisdell's paper on the TGT. (Through to the TGT section of the home page).
Using the TGT as a Platonic protractor
The TGT is also used in the Plato's protractor investigations in the Mathomat Explorer student manual. Here it acts as a model for a mental image of a protractor that students can learn to operate while they develop a robust concept for angle that can support the learning of trigonometry.
The Constructor series
The constructor one template is the first fo series of templates inspired by Chris Tisdell. The Constructor templates have a naked design, which makes minimum use of print. That's because we want the user to focus on geometry, not measurement.
In Constructor one Chris has integrated a large, 25mm radius TGT with a matching radius arc sector and Neusis straight edge.
See how this combination can be used for exploring the world of geometric construction in Chris's new video series (Through to Constructor one videos)