Directional Derivative

Directional Derivative : Derivative of a function along any given specific direction

represents a surface. Directional Derivative of

along the direction of vector

is dot product of

with unit vector along

In the following activity you can change the function

to find directional derivative at the point input

and along the vector

gives direction of maximum change. Significance of Directional Derivative (

): if there is a very small change

in the input

along the direction of vector

, then corresponding change in the output will be

times the

evaluated at