The directional derivative tells us the rate of change given a direction of a unit vector. But how do you get that unit vector?
I know it says that the gradient points to that direction, but I just can't grasp this.
Looking at gradients of a 3-d function it seems they differ by size and direction. The size is the steepness of slope. That one is derived from the dot product the directional vector and the gradient, I believe?
Anyway can somebody can where and how do you get the direction of the vector. Here the directional vector is suposed to be given.