# Very basic partial derivatives problem

1. Dec 29, 2009

### mnb96

Hello,
I should feel ashamed to ask this, but it's giving me (and others) some troubles.

given $$f(x_1,\ldots,x_n)$$, is it wrong to say that:

$$\frac{\partial f}{\partial f}=1$$

...?

2. Dec 29, 2009

### CompuChip

It doesn't make a lot of sense... the idea is that in the expression $\frac{\partial f}{\partial x}$, f is a function and x is a variable on which f does (or does not, or does indirectly) depend.

You can write
$$\frac{\delta f(x_1, \cdots, x_n)}{\delta f(x_1', \cdots, x_n')} = \delta(x_1 - x_1') \cdots \delta(x_n - x_n')$$
where the delta's on the right hand side are Dirac delta distributions, but you are taking functional derivatives then.

3. Dec 29, 2009

### mnb96

uhm...it makes some sense in the following context: