In mathematics, the directional derivative of a multivariate differentiable function along a given vector v at a given point x intuitively represents the instantaneous rate of change of the function, moving through x with a velocity specified by v. It therefore generalizes the notion of a partial derivative, in which the rate of change is taken along one of the curvilinear coordinate curves, all other coordinates being constant.
The directional derivative is a special case of the Gateaux derivative.
The question asks:
Find the directional derivative of f (x, y, z) = z ln (x/y) at (1, 1, 2) toward the point (2, 2, 1).
What I did was find the distance between the two points to be the directional vector (i+j-k) and then I took the norm of the direction vector. so my unit vector =...
"directional derivative" - conventions
Warning: nitpicking notational issues ahead! :eek:
So the "directional derivative" in vector analysis - the differential rate of increase of a scalar function φ in a vector direction - is by convention* defined starting from the vector gradient (the...
Im reading over about the directional derivative.
Stewart, page 800 says:
"Proof: If we define a function g of the single variable h by
g(h) = f(x_0 + ha, y_0 + hb)
then by the definition of a derivative we have
g'(0)= lim_{h \rightarrow 0} \frac{g(h) - g(0)}{h} = lim_{h...