what is multi variable chain rule in differentiation?

Question

anonymous · Answer

chain rule is 
dy/du du/dx = dy/dx
where y = f(u) and u = f(x)
multi-variable?
longer chain?  I don't know.

neo92 · Answer

yeah thtz da problem im having..

anonymous · Answer

sorry

neo92 · Answer

i knw da chain rule.. but wht is multi variable chain rule. is it da same o something else..

neo92 · Answer

this is where i found it

anonymous · Answer

the multivariable chain rule looks like this:

$$f(x,y,z)  $$ For a three dimensional function, then it's derivative is
$$ df=f_xdx+f_ydy+f_zdz  $$ 
not that the indices here state a partial derivative.

anonymous · Answer

I know that one, but there's no chain there

anonymous · Answer

I haven't read the paper fully which you have linked above, but he's talking about a two dimensional function there, where the intention is to solve a differential equation (exact).

$$ df=f_xdx+f_ydy$$ you want a a small change in x

$$ \frac{df}{dx}=f_x+f_y\frac{dy}{dx}$$

anonymous · Answer

and the righthand side is what you have for an exact equation.

anonymous · Answer

@telliott99 http://www.youtube.com/watch?v=7eZVshlT33Q

anonymous · Answer

it clearly depends on the setup, but this is the chain rule for multivariable calculus.

neo92 · Answer

@Spacelimbus and @telliott99 thank both of u very much..

anonymous · Answer

welcome

anonymous · Answer

yw
and thank you @Spacelimbus I have it now.  I'd forgotten