1. The problem statement, all variables and given/known data let V=f(x²+y²) , show that x(∂V/∂y) - y(∂V/∂x) = 0 2. Relevant equations 3. The attempt at a solution V=f(x²+y²) ; V=f(x)² + f(y)² ∂V/∂x = 2[f(x)]f'(x) +  ∂V/∂y = 2[f(y)]f'(y) I'm sure I've gone wrong somewhere, I have never seen functions like this, I'm just used to using V=f(x,y)= some function and then partially differentiations. help would be much apprectiated.