I'm writing documentation for my diagram-drawing tools today, so this tweet by @wtgowers inspired me to draw the diagram he's talking about!
twitter.com/wtgowers/statu…
In reply to @christianp
@wtgowers here's the Numbas Eukleides code I wrote to produce the diagram: gist.github.com/christianp/278…
It's too complicated because I decided to get all the coords by rotation, instead of just typing them in, and the JME Eukleides extension could do with more convenient syntax