Fun With... Gradients! :: f(x,y) = sqrt( 16 - x^2 - y^2 )

mathworld info about gradients

COOL STUFF ABOUT GRADIENTS

- **Note: This applet demonstrates gradients for only one f(x,y), a half sphere with radius 4.**

- Other Note: This is a top down view of the graph, with x going left-right, y going top-bottom.

- A gradient is really just an x,y vector with values of Fx and Fy (directional derivatives).

- The norm of the gradient is equal to the directional derivative in the direction of the gradient.

- Our half sphere is symmetrical; lock your x/y radius from the center and watch Fu...