- #1

- 53

- 0

## Homework Statement

In books I have been using to learn about the Lagrangian function, I find equations that have a derivative of a partial derivative, as in the snippet below. Is there a place where I can learn how this works and *why* it works? I think I can do it mechanically but I want to understand what I am doing. What type of calculus books would have an explanation of it, advanced calculus books?

## Homework Equations

[tex]\frac{d}{dt} (\displaystyle \frac{\partial T}{\partial \dot{q}_\alpha}) [/tex]