Recently I started with multivariable calculus; where I have seen concepts like multivariable function, partial derivative, and so on. A week ago we saw the following concept:(adsbygoogle = window.adsbygoogle || []).push({}); directional derivative. Ok, I know the math behind this as well as the way to compute the directional derivative through the dot product of the gradient and the unit vector:

Duf(x,y)=∇f(x,y)⋅uWhere:

Ok, I know the equation, but my questions are the following:

- Duf(x,y) represents the
directional derivative- ∇f(x,y) represents the
gradient

- u represents the
unit vectorwhat's exactly a directional derivative? what's a gradient? for what are they used?

Thanks.

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# Directional derivative and gradient definition confusion

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