Mathomat V3

# Construct an Equilateral Triangle

video tutorial part
4
of

## Learning Geometry with a Circle Arc Template

with

### Chris Tisdell

Mathematician & Educator

### Materials you will need:

Mathomat V3 Template
Unlined Paper / Scrap Paper
Sharp Pencil/s
Fine-point Pen/s
Eraser

### What you will learn in this tutorial:

In this video presentation, Chris Tisdell introduces a new tool for geometric constructions that replaces traditional compasses. He demonstrates a basic construction, showing how to construct an equilateral triangle on a given line segment using this new tool.

The presentation begins with Chris explaining the motivation behind developing this new tool. Traditional compasses have limitations, including being hard to use, inaccurate, and potentially unsafe. Therefore, the new tool, which combines a circle arc template and a straight edge, was designed as a more practical and precise alternative.

Chris then proceeds to demonstrate the construction step by step:

1. He positions the circle arc template atone endpoint of the given line segment (AB) and draws a 300-degree arc to create a new point (C) where the arc intersects the line segment.
2. The circle arc template is repositioned at point C, and another arc is drawn, this time showing only the intersection point (D).
3. By drawing a straight line through points A and D, Chris forms a smaller equilateral triangle (ABD).
4. This process is repeated on the other endpoint, creating a similar smaller equilateral triangle (CBF).
5. Chris concludes that the triangle ABG is equilateral based on the congruence and similarity of the smaller triangles.
6. He justifies the construction using similar triangles, stating that the ratios of corresponding sides must be equal, thus proving that the constructed triangle is indeed equilateral.

Throughout the presentation, Chris emphasises the historical significance of this construction, mentioning that it is the first challenge in Euclid's ancient book, "The Elements." He also demonstrates the accuracy of the construction by measuring the sides of the triangle.

In summary, Chris Tisdell's presentation introduces a new geometric construction tool designed to replace compasses. He illustrates the construction of an equilateral triangle on a given line segment, emphasising its historical importance and the mathematical concepts behind the construction, such as congruence and similarity of triangles.

### Chris Tisdell

Mathematician & Educator
Chris, a mathematician and educator, is an academic advisor to Mathomat. Chris approached us in 2021 with an interest in the circle templates in Mathomat...
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