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#### References to other Issues or PRs

#29815 should be merged before this PR

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#### Brief description of what is fixed or changed

- Switched two instances of .jacobian to linear_eq_to_matrix in forming Lagranges equations.
- Removed one unnecessary call to .jacobian (due to product rule).
- Improved the docstrings of the equations of motion attributes by adding equation explanations and using common terminology.
- I also discovered a likely bug that negatives the Lagrange multipliers. I'll leave this for now and address that in another PR.

#### Other comments


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#### Release Notes

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  * Added a new solver for logarithmic equations.

* functions
  * Fixed a bug with log of integers. Formerly, `log(-x)` incorrectly gave `-log(x)`.

* physics.units
  * Corrected a semantical error in the conversion between volt and statvolt which
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* physics.mechanics
  * Improved the computational efficiency of forming the equations of motion in `LagrangesMethod`.
* polys
  * Improve computational efficiency of zero terms in _lin_eq2dict and thus linear_eq_to_matrix.

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