# Problem with directional derivative

Hi guys! i have a problem, and i'm unable to solvie it :/
I have this two variable function: it is 0 in {0,0} while it is (x^3 y^2)/(x^2+Abs(y)^(2a)) elsewhere.
do...given the vector {l1,l2} they are asking me: for which "a" the directional derivative along that vector exist in {0,0}? and when it exist what it is? Despite the fact that i know the background theory i'm unable to do the problem, in particular i'm unable to complete the necessary limit :/

SammyS
Staff Emeritus
Homework Helper
Gold Member
Hi guys! i have a problem, and i'm unable to solvie it :/
I have this two variable function: it is 0 in {0,0} while it is (x^3 y^2)/(x^2+Abs(y)^(2a)) elsewhere.
do...given the vector {l1,l2} they are asking me: for which "a" the directional derivative along that vector exist in {0,0}? and when it exist what it is? Despite the fact that i know the background theory i'm unable to do the problem, in particular i'm unable to complete the necessary limit :/
Is this homework?

what do u mean by homework?

SammyS
Staff Emeritus
Homework Helper
Gold Member
what do u mean by homework?
Like - you are taking a course and you have been given some problems to solve .

fresh_42
Mentor
2021 Award
The question looks like as if the homework template should have been used. If you start a thread there - in this case in
https://www.physicsforums.com/forums/calculus-and-beyond-homework.156/
then the template will automatically be applied:

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## The Attempt at a Solution

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Thus, e.g. the definition of the directional derivative would be expected in section 2 and some effort from your side to solve the problem in section 3, i.e. where exactly did you get stuck and why. This is not meant to peeve you! It is meant to lay a common basis on which we can solve the problem together. Don't forget this is internet and the chances are high, that we might misunderstand each other. So the template serves the function of clarification.

• jim mcnamara and SammyS