directional derivative

The rate of increase, of a scalar field $f(x, y, z) = xyz$, in the direction $v = (2,1,2)$ at a point $(0,2,1)$ is

The rate of increase, of a scalar field $$f(x,y,z) = xyz$$, in the direction $$v = (2,1,2)$$ at a point (0,2,1) is

The directional derivative of $$f\left( {x,y} \right) = {{xy} \over {\sqrt 2 }}\left( {x + y} \right)$$ at $$(1, 1)$$ in the direction of the unit vector at an angle of $${\pi \ove...