When you study physics, you never really delve into the reasons behind some of mathematical identities, i was curious about this one as it occurs in Bloch's Theorem (correct me if I go wrong):(adsbygoogle = window.adsbygoogle || []).push({});

[tex]\frac{d}{dt}(\frac{dE}{dk})=\frac{d^{2}E}{dtdk}=\frac{d^{2}E}{dkdt}=(\frac{d^{2}E}{dk^{2}})\frac{dk}{dt}[/tex]

I checked this and the first and last part are equivalent.

Does that mean you can interchange the numerators and denominators freely? (given that the derivative is an operator)

**Physics Forums - The Fusion of Science and Community**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Derivative identity

Loading...

Similar Threads - Derivative identity | Date |
---|---|

I Partial Vector Derivative | Oct 15, 2017 |

I What is the Result of this Partial Derivative | Jun 21, 2017 |

Derivation of an integral identity from the kdv equation. | May 22, 2014 |

**Physics Forums - The Fusion of Science and Community**