Posts Tagged ‘dissections’
Visualisation: More rotating squares
While we’re rotating polygons, here’s another nice visualisation, this time of a linkage of squares that make up a larger square, and rotate around without self-intersecting as you move the slider.
(Source: rotating_square_linkage.ggb)
Just as with the previous visualisation, you can see this just as a source of pretty pictures, like
or you can start asking yourself questions. For example:
- What other ways can we find to connect the small squares together so that they will expand and collapse back into a square without any of the small squares intersecting? How many of these have rotational or reflectional symmetry?
- How can we describe the movement (the locus) and the amount of rotation of the different squares?
- Can we do something similar with other polygons?
- More generally, can we do something like this to move smoothly between different shapes? And what does ’something like this’ mean?
For the second question, we can use the ‘trace’ feature of Geogebra (and all other dynamic geometry programs) to follow the path of particular points, which might give us some idea about how to derive the equations of the points.
On the last point, there are a large category of dissections which involve taking an object, slicing it into a finite number of shapes, and reassembling them into a different shape. There are several in Amusements in Mathematics, a puzzle book by Henry Dudeney from 1917 which I had a part in digitizing for Project Gutenberg. See this section, for example, for a great introduction to dissection puzzles.
Moving further afield, we can do something very similar to this example to demonstrate Pythagoras’ Theorem. That visualisation may appear later this week :).
Tags: Books, dissections, geogebra, visualisations