Derivative of x² Notation: \frac{{df(x)}}{{dx}}

[danago]

Hey. Just a quick simple question. If i have a function such as:
<br /> y = x^2<br />

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

What if the function of x was given as:
<br /> f(x) = x^2 <br />

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:
<br /> \frac{{df(x)}}{{dx}}<br />
?

Would i write:
<br /> \frac{{df}}{{dx}}<br />
?

Does it even matter? Thanks for the quick advice

Dan.

 

[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.

 

[danago]

ok thanks :)

 

[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.

 

[danago]

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

Like this?
<br /> \frac{d}{{dx}}(x^2 ) = 2x<br />

 

[TD]

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

 

[danago]

ok thanks again :)

 

[FrogPad]

Another short hand is:
y = x^2
y_x = 2x
The \frac{dy}{dx} notation is called Leibniz notation. Check out http://en.wikipedia.org/wiki/Leibniz_notation

 

[danago]

Oo thanks frog. I had never really seen that last y_x[/tex] notation.