Simple Gradient Question (funtion of two variables)

xWaffle
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Homework Statement


Find the gradient of the function at the given point. Then sketch the gradient together with the level curve that passes through the point.

g(x,y) = x2/2 - y2/2; (√2, 1)

Homework Equations


∇f = (∂f/∂x)i + (∂f/∂y)j

The Attempt at a Solution


∇g = <x, -y>
∇g(√2, 1) = <√2, -1>
_______________________

Am I done with this solution? Or is there more I need to put for the gradient at the point?

I'm not really sure if this needs to be reduced to a single number or not, I'm guessing that has to do with my lack of understand of the gradient itself. I thought I was supposed to have a direction vector, is it implied the direction vector is just u = i + j if it is not specified?

I also have no idea how to draw what it's asking. I can't visualise any of this.
 
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No, that is the gradient.

You are confusing this with the derivative "in the direction of unit vector v". That is equal to v\cdot \nabla f.
 
Yes, the gradient you calculated is correct.

In order to visualize the gradient in your problem,
depict a two dimensional graph and pick out arbitrary (x,y) points i.e. (2, 3) (0,1) (-1,0) (-1,-1) … and plug those into ∇(g). Use these corresponding vectors to depict the vector field. For example, at (1,0) the resulting vector would be <1,0>. Likewise…

(2,3) <2, -3>
(0,1) <0,-1>
(-1,0) <-1,0>
(-1,-1) ….
…. ….


To draw each vector, begin with the tail at the chosen (x,y) coordinates and move accordingly. For the first vector, begin at (2,3) then move in the positive x direction 2 units, then move down the negative y direction 3 units – there’s your endpoint. As you draw more vectors out, you should start to get an idea of the field’s behavior.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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