I was kind of expecting M208 to be over my head, but so far I’m really surprised at how much material in the first few units of M208 is also covered in MS221, and at how gentle an introduction the Intro Block actually is. Very pleasantly surprised indeed! I’ve been working on Unit I3: Number systems and GTA1: Symmetry this week, and there were only really two new ideas introduced in these, so I feel like I’m getting a nice, steady warm-up session before the really hard stuff starts.

The topic in I3 that I’d never encountered before was equivalence relations. It took me a little while to get my head around the idea (and to stop thinking of the phrase “equivalence class” in its software testing context from M255), but I think I’ve got a fairly good grasp of it now. I even managed to give a coherent explanation of it to Alex, with the help of the “coloured blocks” example from the h2g2 Equivalence Relations page.

The unit about Symmetry introduces the two-line symbol notation for describing symmetries, which I’d never come across before, and to be honest at first I couldn’t really see the point of doing it this way. If I’m going to describe a reflection of a square in the vertical axis, for instance, I’d much rather write {q_{\pi /2}} than

\left( {\begin{array}{*{20}{c}}1 & 2 & 3 & 4  \\4 & 3 & 2 & 1  \\\end{array}} \right).

But later on in the unit, I watched the video section about symmetries of Platonic solids, and it certainly sounds a lot easier to write down the symmetries of a tetrahedron in a two-line symbol than trying to figure out how to represent it in the form {q_\theta }!

Speaking of Platonic solids, I absolutely love the animations of them on the Wikipedia Platonic solid page. I could watch this octahedron spinning all day!

Octahedron
Octahedron image by Cyp, under the Creative Commons Attribution ShareAlike 3.0 License

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