Derivative Notation

1. Jun 6, 2006

danago

Hey. Just a quick simple question. If i have a function such as:
$$y = x^2$$

Id write the derivative of function y with respect to x as:
$$\frac{{dy}}{{dx}} = 2x$$

What if the function of x was given as:
$$f(x) = x^2$$

I know i could write the derivative as f'(x), but how would i write it in the form i used for the first function. Would this be what i should write:
$$\frac{{df(x)}}{{dx}}$$
?

Would i write:
$$\frac{{df}}{{dx}}$$
?

Does it even matter? Thanks for the quick advice

Dan.

2. Jun 6, 2006

TD

Both are used: the first one emphasizes the fact that f is a function of x, the second is of course shorter, which is desirable as well sometimes.

3. Jun 6, 2006

ok thanks :)

4. Jun 6, 2006

3trQN

i would write the f(x) on its own following the d/dx fraction, but its just a matter of personal preference to me.

5. Jun 6, 2006

danago

Like this?
$$\frac{d}{{dx}}(x^2 ) = 2x$$

6. Jun 6, 2006

TD

Yes, this expression is particularly handy when the expression becomes larger.

7. Jun 6, 2006

danago

ok thanks again :)

8. Jun 6, 2006