Just made this: Interactive Unit Circle
Colors? Style? Should it move on its own? Does it teach anything? Can it do it better?
"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman
Maybe it could be a little larger and the green point on the circle has a tangent being drawn through it. How about providing the equation of that tangent.
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
A number by itself is useful, but it is far more useful to know how accurate or certain that number is.