Entropy *S* can be considered as a function of the independent
varaiables *T* and *V*.

i.e., à (3.1)

The differential change in the entropy associated with the simultaneous change in the independent variables can be written as,

From fundamental property relation I,

dividing by *dT* with constant volume restriction,

and, by the definition of C_{V},

Therefore,

From the Maxwell relation 2,

substituting these in Equn.3.2, we obtain,