Formula_14673

\[[f, g]=f_{p} g_{q}-f_{q} g_{p}=\sum_{k=1}^{n}\left(\frac{\partial f}{\partial p_{k}} \frac{\partial g}{\partial q_{k}}-\frac{\partial f}{\partial q_{k}} \frac{\partial g}{\partial p_{k}}\right) .\]