This is cool, but it has some serious numerical issues that ought to be ironed out. I took their example cubic function, and plotted the first, second and third derivatives. The third derivative goes <i>crazy</i> as x goes away from zero. (See screenshot <a href="http://farm6.static.flickr.com/5088/5361267299_a976c64dcb.jpg" rel="nofollow">http://farm6.static.flickr.com/5088/5361267299_a976c64dcb.jp...</a>)
Slick. Could use a way to generate a URL for an equation.<p>EDIT: There is, but it doesn't seem to work e.g.<p><a href="http://graph.tk/#y%3Dsqrt(1-x%5E100)" rel="nofollow">http://graph.tk/#y%3Dsqrt(1-x%5E100)</a><p><a href="http://graph.tk/#y=sqrt(1-x^100)" rel="nofollow">http://graph.tk/#y=sqrt(1-x^100)</a>