4.1. Rotational drawing

It didn’t take much googling to discover that, after subjecting my poor adolescent brain to two years of A-level mathematics, all the trig I’ve ever really needed to know fits quite easily onto the back of a postcard. I scribbled the arcane markings you see in figure 4.1 sometime during my coding adolescence (a period I don’t think I’ve ever really left). I’ve had this card tucked into a book in my office for more than 10 years now, and I’ve never needed much more (although the book it’s tucked into has changed many times).

Figure 4.1. All the trig I’ve ever needed fits on the back of a postcard.