Gradient and directional derivatives (10/9/2008)

1. Main Points

In todays reading I learned about the gradient which is a vector consisting of the partial derivatives fy(x,y) and fx(x,y). These vectors tell us the rate of change in the x and y directions, directional derivatives on the other hand can tell us the rate of change in any direction in the (x,y)-plane.

2. Challenging

The justification for the directional derivative formula was a little hard to follow I thought. The algebraic steps especially, are we expected to learn this justification?

3. Interesting

It was interesting to learn how to calculate directional derivatives, no longer being constrained to rates of change in the x and y directions, but now I can find the rate of change in any direction in the (x,y)-plane.