# I Fundamental Thermodynamics Relation

1. Feb 5, 2017

### Silviu

Hello! I am a bit confused by the formula $dU = TdS - PdV$. If I want to compute for example $\frac{\partial U}{\partial V}$ I obtain $-P$, but how should I proceed to obtain, for example $\frac{\partial U}{\partial P}$ or $\frac{\partial P}{\partial T}$ which are not obvious from the equation? Thank you!

2. Feb 6, 2017

### Staff: Mentor

For those partial derivatives you mention, you need to specify what is being held constant.

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