# Math Help - partial differentiation

1. ## partial differentiation

I have no idea what's going on here, perhaps tell me what topic heading this would fall under so I can look it over?

2. ## Re: partial differentiation

We are given:

$PV=mRT$

hence:

$P=\frac{mRT}{V}\,\therefore\,\frac{\delta P}{\delta V}=-\frac{mRT}{V^2}$

$V=\frac{mRT}{P}\,\therefore\,\frac{\delta V}{\delta T}=\frac{mR}{P}$

$T=\frac{PV}{mR}\,\therefore\,\frac{\delta T}{\delta P}=\frac{V}{mR}$

and so:

$\frac{\delta P}{\delta V}\frac{\delta V}{\delta T}\frac{\delta T}{\delta P}=\left(-\frac{mRT}{V^2} \right)\left(\frac{mR}{P} \right)\left(\frac{V}{mR} \right)=-\frac{mRT}{PV}=-\frac{PV}{PV}=-1$

3. ## Re: partial differentiation

thanks! how did you know which partials to take? can we just go right to left so partial derivatives: P/V then V/T then T/P ?