# Tag Info

If we have a function $f$ that is a function of several variables $p$, $q$, $r$, etc then we can write a total derivative of $f$ as: $$df = \frac{\partial f}{\partial p} \text{d}p + \frac{\partial f}{\partial q} \text{d}q + \frac{\partial f}{\partial r} \text{d}r + \, ...$$ If we're holding all the variables constant except for $p$, so \$\text{d}q = ...