# Homework Help: Problem with partial derivatives

1. Mar 19, 2009

### ak123456

1. The problem statement, all variables and given/known data
suppose that f(x,y)=f(y,x) for all (x,y)$$\in$$R^2 show that
(for partial derivative )
Df/Dx (a,b)=Df/Dy(b,a)
2. Relevant equations

3. The attempt at a solution
i don't know how to start
can i do like this
set g(x,y)=f(y,x)
f o g (x,y) =f(x,y)
then how to continue ?

2. Mar 19, 2009

### Staff: Mentor

Re: proof

Since you don't have much to go on, I'd suggest that you use the definition of the partial derivative for each of the two partials.