Actually, it IS correct but do you understand why? You cannot just say the partial derivatives are 0 because the value of the function is 0. In order to calculate or , you have to vary x while holding y constant and vice-versa. You cannot have "y= -x" for every such point.Second case:
You need to use
Is this right? I would like to know why it isn't, I think its not. Should I think when I consider the second case as I would go in all directions or something like that? cause in other cases where I got defined different functions for a particular point I've used the definition, but in this case I got trajectories. What should I do?
Bye and thanks.