Not directly related, but I just looked at the blog's first entry, "Geometrical look at tangens," and got a real kick out it. I discovered that very same insight (the presence of the tangent in the unit circle) back when I was around sixteen, and it totally rocked my world.

^Hey Ted, is that the sort of thing David Foster Wallace talks about here?

For most of my college career I was a hard-core syntax wienie, a philosophy major with a specialization in math and logic. I was, to put it modestly, quite good at the stuff, mostly because I spent all my free time doing it. Wienieish or not, I was actually chasing a special sort of buzz, a special moment that comes sometimes. One teacher called these moments "mathematical experiences." What I didn't know then was that a mathematical experience was aesthetic in nature, an epiphany in Joyce's original sense. These moments appeared in proof-completions, or maybe algorithms. Or like a gorgeously simple solution to a problem you suddenly see after half a notebook with gnarly attempted solutions. It was really an experience of what I think Yeats called "the click of a well-made box." Something like that. The word I always think of it as is "click."

Yep, that's it (although I was never good enough at math to successfully chase such moments the way Wallace describes).

I remember that, at the time, I had wondered for ages why the word "tangent" was used for this particular trigonometric function. What did a line touching a curve have to do with the ratio between the sine and cosine of an angle? It had previously occurred to me that the tangent of an angle was also the slope of the hypotenuse in the relevant triangle. And then one day I was playing with the unit circle, and in a flash the relationships between all of these became clear.