Then the two terms which contain time derivatives can be combined into a single term.

Mechanical power is also described as the time derivative of work.

So, the formulation in terms of time derivatives is more elegant.

Thus the time derivative of is negative, and will eventually go to zero, leaving us with only the ground state.

This power can be found by taking the time derivative of the stored energy:

The time derivative of is found the same way as for .

Thus, A is seen to be a difference of two vectors with equal time derivatives.

It should not be confused with the time derivative of the entropy.

The steady state response is with all time derivatives set to zero.

The time derivative of a key interest rate can appear.