The gradient is noted by:
∇f
where f is any scalar function.
Expanded, the gradient looks like this:
[∂f/∂x, ∂f/∂y, ∂f/∂z]
If f is only in terms of x and y (i.e. the equation is z =), just use the first two components.
Note: The gradient does not exist at points where the function is asmotic? or undefined.