Question

Given the attached information, how do I identify \[f_x(5,7)
and
f_y(5,7)\]

Answer 1

Ive plugged in what I could to the formula in my book so I've got \[f_u(5,7)=\sqrt2=f_x(5,7)\left(\begin{matrix}1 \\ \sqrt2\end{matrix}\right)+f_y(5,7)\left(\begin{matrix}1 \\ \sqrt2\end{matrix}\right) = gradf(5,7)*u\]

Answer 2

And I think this is the right track, I just have run out of things to plug in, and if this is even the right way to go about it, I fail to see how to go from this, to identifying the directional derivatives.

Answer 3

could someone that knows calculus take a look at the attached problem and my work and tell me if I am on the right track?