# Talk:Nonlinear finite elements/Weak form of heat equation

Hi,

Shouldn't it be instead of ? ( is the heat capacity at constant pressure while is at constant volume. I assume the two dependent variables are pressure and temperature here, not volume and temperature. (The preceding unsigned comment was added by 80.12.88.217 (talk • contribs) 30 April 2013)

Hello, I'd strongly suggest using different notation for vectors (vector functions) and tensors. I assume kappa to be a tensor. Otherwise the first identity cannot be applied to eq. 29. Changing notation would make the example way more readable. Furthermore, Eq. 30 does not constitute a substitution but rather integration over in . Substitution takes place later, in Eq. 33. (The preceding unsigned comment was added by 77.176.41.77 (talk • contribs) 20 November 2015)