Chord

So I was just thrown for a loop by the phrase
"the derivative of a function f at a point x is the limit of the
gradients of a sequence of chords of the graph off"

It makes much more sense once I hit wikipedia http://en.wikipedia.org/wiki/Chord_(geometry)

The chord is just the line between two points and the circle and in this case the derivitive at a point is gradient or slope of the line as the chord shortens till that line is ifinetly small and we are essential dealing with a point.

We also see the sequence of chords since this is the derivative of a function rather than a single point.

Makes sense, the vocab though threw me off for a bit.